I feel like Alice in Wonderland .... still not working ..
sudo apt install build-essential git libpcre2-dev pkg-config libssl-dev bzip2 wget libavahi-client-dev zlib1g-dev libavcodec-dev libavutil-dev libavformat-dev libswscale-dev libavresample-dev gettext cmake libiconv-hook-dev liburiparser-dev debhelper libcurl4-gnutls-dev -y
sudo apt install dvb-apps libva-dev libva-drm1 libva-x11-1 -y
sudo apt install curl -y
git clone -b release/3.4 https://github.com/tvheadend/tvheadend.git
cd tvheadend
$ ./configure --nowerror
Checking support/features
  checking for cc execinfo.h ...                    ok
  checking for cc -mmmx ...                         ok
  checking for cc -msse2 ...                        ok
  checking for cc getloadavg ...                    ok
  checking for cc atomic64 ...                      ok
  checking for py module gzip ...                   ok
  checking for bzip2 ...                            ok
  checking for pkg openssl  ...                     ok
  checking for pkg zlib  ...                        ok
  checking for pkg avahi-client  ...                ok
  checking for cc sys/inotify.h ...                 ok
  checking for pkg libcurl  ...                     ok
  fetching dvb-scan files ...                       ok
Compiler:
  Using C compiler:                        cc
  Build for arch:                          x86_64
Binaries:
  Using PYTHON:                            python
Options:
  cwc                                      yes
  v4l                                      yes
  linuxdvb                                 yes
  dvbscan                                  yes
  timeshift                                yes
  imagecache                               yes
  avahi                                    yes
  zlib                                     yes
  libav                                    no
  inotify                                  yes
  bundle                                   no
  dvbcsa                                   no
  execinfo                                 yes
  mmx                                      yes
  sse2                                     yes
  getloadavg                               yes
  atomic64                                 yes
  py_gzip                                  yes
  bin_bzip2                                yes
  ssl                                      yes
  inotify_h                                yes
Packages:
  openssl                                  1.1.0f
  zlib                                     1.2.8
  avahi-client                             0.6.32
  libcurl                                  7.52.1
Installation paths:
  Prefix:                                  /usr/local
  Binaries:                                ${prefix}/bin
  Libraries:                               ${prefix}/lib
  Data files:                              ${prefix}/share
  Man pages:                               ${datadir}/man
Final Binary:
  /home/0dBi/git/tvheadend/build.linux/tvheadend
Tvheadend Data Directory:
  /usr/local/share/tvheadend
~/git/tvheadend$ make -k
CC              build.linux/src/main.o
CC              build.linux/src/utils.o
CC              build.linux/src/wrappers.o
CC              build.linux/src/access.o
CC              build.linux/src/dtable.o
CC              build.linux/src/tcp.o
CC              build.linux/src/http.o
CC              build.linux/src/notify.o
CC              build.linux/src/epg.o
CC              build.linux/src/epgdb.o
CC              build.linux/src/epggrab.o
CC              build.linux/src/spawn.o
CC              build.linux/src/packet.o
CC              build.linux/src/streaming.o
CC              build.linux/src/teletext.o
CC              build.linux/src/channels.o
CC              build.linux/src/subscriptions.o
CC              build.linux/src/service.o
CC              build.linux/src/psi.o
CC              build.linux/src/parsers.o
CC              build.linux/src/parser_h264.o
CC              build.linux/src/parser_latm.o
CC              build.linux/src/tsdemux.o
CC              build.linux/src/htsp_server.o
CC              build.linux/src/serviceprobe.o
CC              build.linux/src/htsmsg.o
/home/0dBi/git/tvheadend/src/htsmsg.c: In function ‘htsmsg_print0’:
/home/0dBi/git/tvheadend/src/htsmsg.c:577:7: error: this ‘for’ clause does not guard... [-Werror=misleading-indentation]
       for(i = 0; i < indent; i++) printf("\t"); printf("}\n");
       ^~~
/home/0dBi/git/tvheadend/src/htsmsg.c:577:49: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘for’
       for(i = 0; i < indent; i++) printf("\t"); printf("}\n");
                                                 ^~~~~~
/home/0dBi/git/tvheadend/src/htsmsg.c:583:7: error: this ‘for’ clause does not guard... [-Werror=misleading-indentation]
       for(i = 0; i < indent; i++) printf("\t"); printf("}\n");
       ^~~
/home/0dBi/git/tvheadend/src/htsmsg.c:583:49: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘for’
       for(i = 0; i < indent; i++) printf("\t"); printf("}\n");
                                                 ^~~~~~
cc1: all warnings being treated as errors
Makefile:254: recipe for target 'build.linux/src/htsmsg.o' failed
make: *** [build.linux/src/htsmsg.o] Error 1
CC              build.linux/src/htsmsg_binary.o
CC              build.linux/src/htsmsg_json.o
CC              build.linux/src/htsmsg_xml.o
CC              build.linux/src/misc/dbl.o
CC              build.linux/src/misc/json.o
CC              build.linux/src/settings.o
CC              build.linux/src/htsbuf.o
CC              build.linux/src/trap.o
CC              build.linux/src/avg.o
CC              build.linux/src/htsstr.o
CC              build.linux/src/rawtsinput.o
CC              build.linux/src/iptv_input.o
CC              build.linux/src/avc.o
CC              build.linux/src/huffman.o
CC              build.linux/src/filebundle.o
CC              build.linux/src/config2.o
CC              build.linux/src/lang_codes.o
CC              build.linux/src/lang_str.o
CC              build.linux/src/imagecache.o
CC              build.linux/src/tvhtime.o
CC              build.linux/src/epggrab/module.o
CC              build.linux/src/epggrab/channel.o
CC              build.linux/src/epggrab/module/pyepg.o
CC              build.linux/src/epggrab/module/xmltv.o
CC              build.linux/src/plumbing/tsfix.o
CC              build.linux/src/plumbing/globalheaders.o
CC              build.linux/src/dvr/dvr_db.o
CC              build.linux/src/dvr/dvr_rec.o
CC              build.linux/src/dvr/dvr_autorec.o
CC              build.linux/src/webui/webui.o
CC              build.linux/src/webui/comet.o
CC              build.linux/src/webui/extjs.o
CC              build.linux/src/webui/simpleui.o
CC              build.linux/src/webui/statedump.o
CC              build.linux/src/webui/html.o
CC              build.linux/src/muxer.o
CC              build.linux/src/muxer/muxer_pass.o
CC              build.linux/src/muxer/muxer_tvh.o
CC              build.linux/src/muxer/tvh/ebml.o
CC              build.linux/src/muxer/tvh/mkmux.o
CC              build.linux/src/epggrab/otamux.o
CC              build.linux/src/epggrab/module/eit.o
/home/0dBi/git/tvheadend/src/epggrab/module/eit.c: In function ‘_eit_get_string_with_len’:
/home/0dBi/git/tvheadend/src/epggrab/module/eit.c:215:3: error: this ‘else’ clause does not guard... [-Werror=misleading-indentation]
   else
   ^~~~
/home/0dBi/git/tvheadend/src/epggrab/module/eit.c:217:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘else’
     if (m && m->enabled) cptr = _eit_freesat_conv;
     ^~
cc1: all warnings being treated as errors
Makefile:254: recipe for target 'build.linux/src/epggrab/module/eit.o' failed
make: *** [build.linux/src/epggrab/module/eit.o] Error 1
CC              build.linux/src/epggrab/module/opentv.o
CC              build.linux/src/epggrab/support/freesat_huffman.o
CC              build.linux/src/timeshift.o
CC              build.linux/src/timeshift/timeshift_filemgr.o
CC              build.linux/src/timeshift/timeshift_writer.o
CC              build.linux/src/timeshift/timeshift_reader.o
CC              build.linux/src/dvb/dvb.o
CC              build.linux/src/dvb/dvb_support.o
CC              build.linux/src/dvb/dvb_charset.o
CC              build.linux/src/dvb/dvb_fe.o
CC              build.linux/src/dvb/dvb_tables.o
CC              build.linux/src/dvb/diseqc.o
CC              build.linux/src/dvb/dvb_adapter.o
CC              build.linux/src/dvb/dvb_multiplex.o
CC              build.linux/src/dvb/dvb_service.o
CC              build.linux/src/dvb/dvb_preconf.o
CC              build.linux/src/dvb/dvb_satconf.o
CC              build.linux/src/dvb/dvb_input_filtered.o
CC              build.linux/src/dvb/dvb_input_raw.o
CC              build.linux/src/webui/extjs_dvb.o
CC              build.linux/src/muxes.o
CC              build.linux/src/dvr/dvr_inotify.o
CC              build.linux/src/v4l.o
CC              build.linux/src/webui/extjs_v4l.o
CC              build.linux/src/avahi.o
CC              build.linux/src/cwc.o
CC              build.linux/src/capmt.o
CC              build.linux/src/ffdecsa/ffdecsa_interface.o
CC              build.linux/src/ffdecsa/ffdecsa_int.o
CC              build.linux/src/ffdecsa/ffdecsa_mmx.o
CC              build.linux/src/ffdecsa/ffdecsa_sse2.o
make: Target 'all' not remade because of errors.
so let's try something else:
nano Makefile
CTRL+W: -Werror
CFLAGS  += -Wall -Werror -Wwrite-strings -Wno-deprecated-declarations
[THIS IS THE ONLY OCCURRENCE]
So I have removed the "-Werror" and Bingo it worked :) THANK YOU.
CFLAGS  += -Wall -Wwrite-strings -Wno-deprecated-declarations
Back to building *.deb packages as this would install hopefully all the auto start scripts,
so when restarted this headless PC, I would not have to run "nohup ~/Install/tvheadend-3.4/build.linux/tvheadend -C --http_port 9981 &"
cd ~git/tvheadend/
nano Makefile
CFLAGS  += -Wall -Wwrite-strings -Wno-deprecated-declarations
$ ./Autobuild.sh
target (-t) not specified
so I tried viewing the script:
$ cat Autobuild.sh 
#!/bin/bash
#
# Entry point for the Doozer autobuild system
#
# (c) Andreas Öman 2011. All rights reserved.
#
#
set -eu
BUILD_API_VERSION=3
EXTRA_BUILD_NAME=""
JARGS=""
JOBSARGS=""
TARGET=""
RELEASE="--release"
WORKINGDIR="/var/tmp/showtime-autobuild"
OP="build"
while getopts "vht:e:j:w:o:c:" OPTION
do
  case $OPTION in
      v)
	  echo $BUILD_API_VERSION
	  exit 0
	  ;;
      h)
	  echo "This script is intended to be used by the autobuild system only"
	  exit 0
	  ;;
      t)
	  TARGET="$OPTARG"
	  ;;
      e)
	  EXTRA_BUILD_NAME="$OPTARG"
	  ;;
      j)
	  JOBSARGS="--jobs=$OPTARG"
	  JARGS="-j$OPTARG"
	  ;;
      w)
	  WORKINGDIR="$OPTARG"
	  ;;
      o)
	  OP="$OPTARG"
	  ;;
  esac
done
if [[ -z $TARGET ]]; then
    echo "target (-t) not specified"
    exit 1
fi
#
# $1 = local file path
# $2 = type
# $3 = content-type
# $4 = filename
#
artifact() {
    echo "doozer-artifact:$PWD/$1:$2:$3:$4"
}
versioned_artifact() {
    echo "doozer-versioned-artifact:$PWD/$1:$2:$3:$4"
}
if [ -f Autobuild/${TARGET}.sh ]; then
    source Autobuild/${TARGET}.sh
else
    echo "target $TARGET not supported"
    exit 1
fi
but noting obvious over here ..