add osx build job

.github/workflows/build.yml

@@ -41,6 +41,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v1
       - name: Set outputs for pkg_ver
+        id: set_vars
         run: |
           export ELECTRUM_VERSION=`./contrib/print_electrum_version.py`
           echo "::set-output name=pkg_ver::$(echo $ELECTRUM_VERSION)"
@@ -57,6 +58,31 @@ jobs:
           asset_name: Electrum-${{ github.ref_name }}.tar.gz
           asset_content_type: application/octet-stream
 
+  build_osx:
+    needs: create_release
+    runs-on: macos-11.7
+    name: create release for macOS
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+      - name: Set outputs for pkg_ver
+        id: set_vars
+        run: |
+          export ELECTRUM_VERSION=`./contrib/print_electrum_version.py`
+          echo "::set-output name=pkg_ver::$(echo $ELECTRUM_VERSION)"
+      - name: Build dmg
+        run: |
+          ./contrib/osx/make_osx.sh
+      - name: Upload Release Asset
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ needs.create_release.outputs.upload_url }}
+          asset_path: dist/electrum-${{ steps.set_vars.outputs.pkg_ver }}.dmg
+          asset_name: electrum-${{ steps.set_vars.outputs.pkg_ver }}.dmg
+          asset_content_type: application/apple-diskimage
+
   build_appimage:
     needs: create_release
     runs-on: ubuntu-20.04