actions: vendor sources with submodules for releases

.github/workflows/source-vendor.yml

@@ -0,0 +1,28 @@
+name: Checkout and Create Clean Tarball
+
+on: [push, pull_request]
+
+jobs:
+  create-clean-tarball:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository with submodules
+        uses: actions/checkout@v3
+        with:
+          submodules: 'recursive'
+
+      - name: Create clean tarball
+        run: |
+          git archive --format=tar HEAD -o yosys-src-vendored.tar
+          git submodule foreach '
+            git archive --format=tar --prefix="${sm_path}/" HEAD --output=${toplevel}/vendor-${name}.tar
+          '
+          tar --concatenate --file=yosys-src-vendored.tar vendor-*.tar
+          gzip yosys-src-vendored.tar
+
+      - name: Store tarball artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: clean-sources-tarball
+          path: yosys-src-vendored.tar.gz
+          retention-days: 1

.gitmodules

@@ -1,6 +1,7 @@
 [submodule "abc"]
 	path = abc
 	url = https://github.com/YosysHQ/abc
-[submodule "libs/cxxopts"]
+# Don't use paths as names to avoid git archive problems
+[submodule "cxxopts"]
 	path = libs/cxxopts
 	url = https://github.com/jarro2783/cxxopts