util/u_thread: fix compilation on Mac OS

Apparently, it doesn't have pthread barriers.

p_config.h (which was originally used to guard this code) uses the
__APPLE__ macro to detect Mac OS.

Fixes: f0d3a4de75 ("util: move pipe_barrier into src/util and rename to util_barrier")
Cc: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
1 file changed