add script and compose file for mcu builds

docker-compose.mcu.yaml

@@ -0,0 +1,11 @@
+services:
+  make:
+    image: mkuf/klipper:nightly-mcu
+    tty: true
+    privileged: true
+    entrypoint: make
+    working_dir: /opt/klipper
+    volumes:
+      - /dev:/dev
+      - ./config/build.config:/opt/klipper/.config
+      - ./out:/opt/klipper/out

scripts/build-mcu.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+docker compose -f docker-compose.mcu.yaml run --rm make "${@}"