ci: add workflow with smoke-build in kas

The workflow is sa straightforward kas build with a github cache
on downloads and layers. Caching sstate-cache is desired but impossible
due to the 10GB limit imposed by GitHub.

Signed-off-by: Zygmunt Krynicki <[email protected]>

.github/workflows/kas.yml

@@ -0,0 +1,35 @@
+name: kas build
+on:
+  pull_request:
+    branches: [ "master", "kirkstone" ]
+  push:
+    branches: [ "master", "kirkstone", "workflow"]
+
+jobs:
+  kas:
+    runs-on: ubuntu-22.04
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+    - name: Install build dependencies
+      run: |
+        sudo apt-get update
+        sudo -E DEBIAN_FRONTEND=noninteractive apt install -y kas chrpath diffstat
+    - name: Cache meta-layers
+      uses: actions/cache@v4
+      with:
+        path: layers
+        key: master-layers
+        save-always: true
+    - name: Cache downloads
+      uses: actions/cache@v4
+      with:
+        path: build/downloads
+        key: master-downloads
+        save-always: true
+    - name: Kas checkout
+      run: |
+        kas checkout kas-poky-snapd.yml
+    - name: Kas build
+      run: |
+        kas build kas-poky-snapd.yml