[build] add --with-sanitizers= option for sanitizer builds (#366)

this option is stricly meant for runtime debugging purposes.
do NOT use in production.

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

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

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