Adding a release workflow.

.github/workflows/build-release.yml

@@ -0,0 +1,39 @@
+name: Release
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  ci:
+    name: CI
+    uses: ./.github/workflows/ci.yml
+    with:
+      release_build: true
+
+  release:
+    name: Release
+    needs: ci
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Code Checkout
+        uses: actions/checkout@v2
+
+      - name: Fetch build artifacts
+        uses: actions/download-artifact@v2
+
+      - name: List assets
+        run: ls -al Assets
+
+      - name: Attach assets to release
+        run: |
+          set -x
+          assets=()
+          for asset in Assets/*.hex; do
+            assets+=("-a" "$asset")
+            echo "$asset"
+          done
+          tag_name="${GITHUB_REF##*/}"
+          hub release edit "${assets[@]}" -m "" "$tag_name"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/ci.yml

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+# Builds Betaflight Firmware.
+#
+# After building, artifacts are kept for 7 days.
+
+name: CI
+
+on: 
+  workflow_call:
+    inputs:
+      release_build:
+        description: 'Specifies if it is a debug build or a release build'
+        default: false
+        required: false
+        type: boolean
+
+jobs:
+  build:
+    name: Build
+    runs-on:  ubuntu-20.04
+    steps:
+      - name: Code Checkout
+        uses: actions/checkout@v2
+
+      - name: Prepare environment
+        run: make arm_sdk_install
+
+      - name: Execute Build
+        run: make all RELEASE=${{ inputs.release_build && 'yes' || 'no' }}
+
+      - name: Publish build artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: Assets
+          path: ./obj/*.hex
+          retention-days: 7