util: fix compilation on macos
timespec_get() is not available on macos, we need to pull in the include/c11/threads_posix.h helper.
Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103674 Fixes: e2d761de ("util: drop final reference to p_compiler.h")