Add CI run for building upb Python wheels

This restores a CI run that used to exist in the upb repo. I still need to add
test runs to exercise the wheels, but this change adds the functionality for
building and uploading them.

PiperOrigin-RevId: 564896637

.github/workflows/test_upb.yml

@@ -119,3 +119,31 @@ jobs:
             mv `which python3` /tmp &&
             ! which python3 &&
             bazel test $BAZEL_FLAGS --cxxopt=-std=c++17 --host_cxxopt=-std=c++17 //upb/python/... -- -//upb/python/dist:source_wheel
+
+  build_wheels:
+    name: Build Wheels
+    runs-on: ubuntu-latest
+    if: ${{ github.event_name == 'pull_request' }}
+    steps:
+      - name: Checkout pending changes
+        uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
+        with:
+          ref: ${{ inputs.safe-checkout }}
+      - name: Build Wheels
+        uses: protocolbuffers/protobuf-ci/bazel-docker@v2
+        with:
+          image: us-docker.pkg.dev/protobuf-build/release-containers/linux/apple@sha256:bb1d14738449916d489c1cbb062508c4dca5bd265ea3e67a2628ae40912b9b00
+          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
+          bazel-cache: upb-bazel-python
+          bazel: build --crosstool_top=//toolchain:clang_suite --//toolchain:release=true --symlink_prefix=/ -c dbg //upb/python/dist //upb/python/dist:test_wheel //upb/python/dist:source_wheel
+      - name: Move Wheels
+        run: mkdir wheels && find _build/out \( -name 'protobuf*.whl' -o -name 'protobuf-*.tar.gz' \) -exec mv '{}' wheels ';'
+      - uses: actions/upload-artifact@v3
+        with:
+          name: python-wheels
+          path: wheels/
+      - uses: actions/upload-artifact@v3
+        with:
+          name: requirements
+          # Tests shouldn't have access to the whole upb repo, upload the one file we need
+          path: upb/python/requirements.txt

upb/bazel/python_downloads.bzl

@@ -39,7 +39,7 @@ cc_import(
     hdrs = glob(["**/*.h"]),
     shared_library = "python{0}.dll",
     interface_library = "libs/python{0}.lib",
-    visibility = ["@upb//python:__pkg__"],
+    visibility = ["@com_google_protobuf//upb/python:__pkg__"],
 )
 
 cc_import(
@@ -47,7 +47,7 @@ cc_import(
     hdrs = glob(["**/*.h"]),
     shared_library = "python{1}.dll",
     interface_library = "libs/python{1}.lib",
-    visibility = ["@upb//python:__pkg__"],
+    visibility = ["@com_google_protobuf//upb/python:__pkg__"],
 )
 """