Use pthread calls instead of raw syscalls on non-Linux systems

Raw system calls aren't portable to other kernels.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/drm_import_export.c

@@ -121,7 +121,11 @@ static void start_test(void)
 
 static void * test_thread(void * par)
 {
+#ifdef __linux__
 	igt_debug("start %ld\n", syscall(SYS_gettid));
+#else
+	igt_debug("start %ld\n", (long) pthread_self());
+#endif
 	start_test();
 
 	return NULL;