lib/fuzzing/oss-fuzz: Add build_samba.sh for oss-fuzz

lib/fuzzing/oss-fuzz: Add build_samba.sh for oss-fuzz

We work hard to put the primary logic for oss-fuzz here, and
where possible into waf, so that only a tiny stub needs to
be maintained in the Google oss-fuzz repo.

This will be called by build.sh (not copied directly because
it is too easy to forget to copy in an updated version when
doing development in the docker image).

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Uri Simchoni <uri@samba.org>