[build] add github cache workflow with cache-save parameter

Author: titusfortner

.github/workflows/bazel.yml

@@ -71,6 +71,11 @@ on:
         required: false
         type: string
         default: ''
+      cache-save:
+        description: Save the Bazel cache after the run (avoids multiple jobs clobbering it)
+        required: false
+        type: boolean
+        default: false
       gem-trusted-publishing:
         description: Exchange GitHub OIDC token for a RubyGems API token (requires trusted publisher configured on rubygems.org)
         required: false
@@ -156,7 +161,7 @@ jobs:
         continue-on-error: true
         uses: bazel-contrib/setup-bazel@0.19.0
         with:
-          cache-save: ${{ github.ref_name == 'trunk' }}
+          cache-save: ${{ inputs.cache-save }}
           bazelisk-cache: true
           bazelrc: common --color=yes
           # Workaround for long path issues: https://github.com/bazelbuild/bazel/pull/22532

.github/workflows/ci-rbe.yml

@@ -29,6 +29,7 @@ jobs:
     uses: ./.github/workflows/bazel.yml
     with:
       name: All RBE tests
+      cache-save: ${{ github.ref_name == 'trunk' }}
       rerun-with-debug: true
       ruby-version: jruby-10.1.0.0
       run: ./scripts/github-actions/ci-build.sh ${{ github.event.inputs.disable_test_cache }}

.github/workflows/gh-cache.yml

@@ -0,0 +1,28 @@
+name: CI Cache
+
+on:
+  workflow_dispatch:
+
+concurrency:
+  group: ci-cache-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  populate:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos, windows]
+    uses: ./.github/workflows/bazel.yml
+    with:
+      name: Populate cache (${{ matrix.os }})
+      os: ${{ matrix.os }}
+      cache-save: false
+      run: >
+        bazel build --nobuild --build_tests_only --keep_going
+        --repository_contents_cache=
+        //java/... //py/... //rb/... //rust/...
+        //javascript/selenium-webdriver/... //dotnet/...