add a daily cron and general build action for github actions

.github/workflows/daily.yaml

@@ -0,0 +1,34 @@
+name: Daily Build and trunk tester
+on:
+  push:
+    branches: [ $default-branch ]
+  schedule:
+    - cron: "0 7 * * *"   # daily 07:00
+  workflow_dispatch: {}
+
+jobs:
+  debian_update:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout (if needed)
+        uses: actions/checkout@v4
+      
+      - name: Update and install build tools and deps
+        run: |
+          bash -c "apt update && apt upgrade -y"
+          apt install -y build-essential nasm mtools fdisk dosfstools 
+
+      - name: Build stevia
+        run: make
+
+      - name: Upload build artifacts
+        if: always()   # still keep logs/artifacts even if build fails
+        uses: actions/upload-artifact@v3
+        with:
+          name: stevia-${{ github.run_number }}
+          path: |
+            build/output/artifacts.tar.gz
+            build/output/disk.img.gz
+            build/output/part.img.gz
+          if-no-files-found: error
+          retention-days: 7   # override server default if you like