tests: Only run buffer-count test if we have at least mesa 10

https://bugs.freedesktop.org/show_bug.cgi?id=72835
diff --git a/tests/weston-test-client-helper.c b/tests/weston-test-client-helper.c
index fd265f2..399aa44 100644
--- a/tests/weston-test-client-helper.c
+++ b/tests/weston-test-client-helper.c
@@ -496,6 +496,20 @@
 	handle_global
 };
 
+void
+skip(const char *fmt, ...)
+{
+	va_list argp;
+
+	va_start(argp, fmt);
+	vfprintf(stderr, fmt, argp);
+	va_end(argp);
+
+	/* automake tests uses exit code 77, but we don't have a good
+	 * way to make weston exit with that from here. */
+	exit(0);
+}
+
 static void
 log_handler(const char *fmt, va_list args)
 {