build: add option for enabling sanitizer builds

--with-sanitizers= option is stricly meant for runtime debugging
purposes. Do NOT use in production.

Please check gcc/clang man pages on how to use ASAN/UBSAN/TSAN.

Also allow users to specificy SANITIZERS_CFLAGS and SANITIZERS_LDFLAGS
for advanced use.

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>