[swift] Add a GitHub Actions workflow for distribution

.github/workflows/build-swift-debugging.yaml

@@ -0,0 +1,21 @@
+name: Build Swift Debugging Extension
+on:
+  push:
+    branches:
+      - swift-debugging
+jobs:
+  build-extension:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: 'recursive'
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+      - run: ./tools/bootstrap.py ../../out -no-check -release-version 90001 -patch-level 0
+        working-directory: ./extensions/cxx_debugging/
+      - uses: actions/upload-artifact@v4
+        with:
+          name: cxx_debugging_extension
+          path: ./out/DevTools_CXX_Debugging.stage2/cxx_debugging_extension-*.zip