Skip tests that require a filesystem that obeys POSIX permissions

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 5337e89..f134e73 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -687,6 +687,10 @@
 	pwd () {
 		builtin pwd -W
 	}
+	# no POSIX permissions
+	;;
+*)
+	test_set_prereq POSIXPERM
 	;;
 esac