ci: add a m1n1 build CI job

Uploads the build m1n1.macho and compiled device tree.

Signed-off-by: Janne Grunau <j@jannau.net>

.github/workflows/build.yml

@@ -0,0 +1,35 @@
+# This is a basic workflow to help you get started with Actions
+
+name: build
+
+# Controls when the action will run.
+on:
+  # Triggers the workflow on push or pull request events but only for the main branch
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: recursive
+    - name: install aarch64-linux-gnu- toolchain
+      run: |
+        sudo apt-get update
+        sudo apt-get install --no-install-recommends -y device-tree-compiler gcc-aarch64-linux-gnu
+    - name: build
+      run: make -k -j2 ARCH=aarch64-linux-gnu-
+    - uses: actions/upload-artifact@v2
+      with:
+        name: m1n1
+        path: |
+          build/m1n1.macho
+          build/dtb/t8103-j274.dtb