tools: Patch libtool to pass-through sanitizer flags

This is a backport of
http://git.savannah.gnu.org/cgit/libtool.git/commit/?id=a5c6466
as libtool has no release that includes this commit, yet.

It fixes using sanitizers on macOS, as without this patch, the
relevant flag is not passed to the compiler when linking, causing
undefined symbol errors.