build: Fix gitlab CI configuration

Run «apt install» in non-interactive mode, and do not install
Recommends. Replace build-essential, which is rather fat, with gcc
and make. Execute autogen instead of autoreconf directly.
3 jobs for master in 23 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Autogen
failed #955
autogen

00:00:23

 
  Build
skipped #956
build
 
  Test
skipped #957
test
 
Name Stage Failure
failed
autogen Autogen
./get-version: 37: ./get-version: git: not found
configure.ac:9: error: AC_INIT should be called with package and version arguments
/usr/share/aclocal-1.15/init.m4:29: AM_INIT_AUTOMAKE is expanded from...
configure.ac:9: the top level
autom4te: /usr/bin/m4 failed with exit status: 1
aclocal: error: echo failed with exit status: 1
autoreconf: aclocal failed with exit status: 1
/bin/bash: line 63: ./configure: No such file or directory
ERROR: Job failed: exit code 1