build,tests: Run t-lock-single-posix only on platforms supported.
* configure.ac (HAVE_LOCK_OPTIMIZATION): New. * tests/Makefile.am: Use HAVE_LOCK_OPTIMIZATION for t-lock-single-posix.
- GnuPG-bug-id: T5699
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>