Q: Why is firmware build is failing at ./bin/automake.tmp line 3938?

touch /root/carambola2/build_dir/host/automake-1.15/.prepared47bfd06f9c2eb23a9dd6544caff8de43
(cd /root/carambola2/build_dir/host/automake-1.15; AUTOM4TE=/root/carambola2/staging_dir/host/bin/autom4te AUTOCONF=/root/carambola2/staging_dir/host/bin/autoconf AUTOMAKE=/root/carambola2/staging_dir/host/bin/automake ACLOCAL=/root/carambola2/staging_dir/host/bin/aclocal AUTOHEADER=/root/carambola2/staging_dir/host/bin/autoheader LIBTOOLIZE=/root/carambola2/staging_dir/host/bin/libtoolize LIBTOOL=/root/carambola2/staging_dir/host/bin/libtool M4=/root/carambola2/staging_dir/host/bin/m4 AUTOPOINT=true STAGING_DIR="" ./bootstrap.sh)
Unescaped left brace in regex is illegal here in regex; marked by <-- HERE in m/\${ <-- HERE ([^ \t=:+{}]+)}/ at ./bin/automake.tmp line 3938.
Makefile:50: recipe for target '/root/carambola2/build_dir/host/automake-1.15/.configured' failed
make[3]: *** [/root/carambola2/build_dir/host/automake-1.15/.configured] Error 255
make[3]: Leaving directory '/root/carambola2/tools/automake'
tools/Makefile:134: recipe for target 'tools/automake/compile' failed

A: You are most likely building on Ubuntu 18.04 which is not supported by our build system. Solution would be to use older Ubuntu. 16.04LTS version works just fine.