basic/path-util: allow flags for path_equal_or_files_same

No functional change, just a new parameters and the tests that
AT_SYMLINK_NOFOLLOW works as expected.

src/basic/virt.c

@@ -574,7 +574,7 @@ int running_in_chroot(void) {
         if (getenv_bool("SYSTEMD_IGNORE_CHROOT") > 0)
                 return 0;
 
-        ret = files_same("/proc/1/root", "/");
+        ret = files_same("/proc/1/root", "/", 0);
         if (ret < 0)
                 return ret;