scripts/build_mt: trivial multithreaded wrapper for ad-hoc packages

scripts/build_mt

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019-present Team LibreELEC (https://libreelec.tv)
+
+. config/options ""
+. config/multithread
+
+# Setup both toolchain cmake configs to avoid potentially racy behaviour later.
+# Use a fork for host to isolate any variable modifications.
+( setup_toolchain host )
+setup_toolchain target
+
+MTADDONBUILD=no start_multithread_build ${@}