chore: Add a CI check to run the macOS distributable binary.

We run it on a pristine macOS instance without anything we may have done
to the build instance.

.github/workflows/build-test-deploy.yaml

@@ -382,6 +382,28 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           artifacts: "qTox-nightly-${{ matrix.arch }}.dmg,qTox-nightly-${{ matrix.arch }}.dmg.sha256"
 
+  test-macos-distributable:
+    name: Test macOS distributable
+    needs: build-macos-distributable
+    strategy:
+      matrix:
+        arch: [arm64]
+    runs-on: ${{ matrix.arch == 'arm64' && 'macos-14' || 'macos-13' }}
+    permissions:
+      contents: write
+    steps:
+      - name: Download artifact from macOS distributable (${{ matrix.arch }})
+        uses: actions/download-artifact@v4
+        with:
+          name: qTox-${{ github.sha }}-${{ matrix.arch }}.dmg
+          path: qTox.dmg
+      - name: Install 7zip
+        run: brew install 7zip
+      - name: Unpack dmg
+        run: 7z x qTox.dmg qtox.app
+      - name: Run qTox
+        run: qtox.app/Contents/MacOS/qTox --help
+
   build-macos-user:
     name: macOS user
     if: github.event_name == 'pull_request'