selftests: sync: Skip the test if kernel support is not found

The "Sync framework" test doesn't work if the kernel has no support,
obviously. Rather than reporting a failure, check for the kernel support
by looking for /sys/kernel/debug/sync/sw_sync, and if not found skip the
test.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/sync/sync_test.c

@@ -29,6 +29,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <sys/wait.h>
 
 #include "synctest.h"
@@ -52,10 +53,22 @@ static int run_test(int (*test)(void), char *name)
 	exit(test());
 }
 
+static int sync_api_supported(void)
+{
+	struct stat sbuf;
+
+	return 0 == stat("/sys/kernel/debug/sync/sw_sync", &sbuf);
+}
+
 int main(void)
 {
 	int err = 0;
 
+	if (!sync_api_supported()) {
+		printf("SKIP: Sync framework not supported by kernel\n");
+		return 0;
+	}
+
 	printf("[RUN]\tTesting sync framework\n");
 
 	err += RUN_TEST(test_alloc_timeline);