Add github action to run bazel build //generator/...

.github/workflows/ci.bazelrc

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+# This file contains Bazel settings to apply on CI only.
+# It is referenced with a --bazelrc option in the call to bazel in ci.yaml
+
+# Debug where options came from
+build --announce_rc
+# This directory is configured in GitHub actions to be persisted between runs.
+build --disk_cache=~/.cache/bazel
+build --repository_cache=~/.cache/bazel-repo
+# Don't rely on test logs being easily accessible from the test runner,
+# though it makes the log noisier.
+test --test_output=errors
+# Allows tests to run bazelisk-in-bazel, since this is the cache folder used
+test --test_env=XDG_CACHE_HOME

.github/workflows/ci.yaml

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+name: CI
+
+# Controls when the action will run.
+on:
+  # Triggers the workflow on push or pull request events but only for the main branch
+  push:
+    branches: [main, es6]
+  pull_request:
+    branches: [main, es6]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+concurrency:
+    # Cancel previous actions from the same PR: https://stackoverflow.com/a/72408109
+    group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+    cancel-in-progress: true
+
+jobs:
+  # matrix-prep-* steps generate JSON used to create a dynamic actions matrix.
+  # Insanely complex for how simple this requirement is inspired from
+  # https://stackoverflow.com/questions/65384420/how-to-make-a-github-action-matrix-element-conditional
+
+  matrix-prep-bazelversion:
+    # Prepares the 'bazelversion' axis of the test matrix
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - id: bazel_from_bazelversion
+        run: echo "bazelversion=$(head -n 1 .bazelversion)" >> $GITHUB_OUTPUT
+      # bazel 5 testing disabled for now due to
+      # https://github.com/aspect-build/bazel-lib/issues/392
+      # - id: bazel_5
+      #   run: echo "bazelversion=5.3.2" >> $GITHUB_OUTPUT
+    outputs:
+      # Will look like ["<version from .bazelversion>"]
+      bazelversions: ${{ toJSON(steps.*.outputs.bazelversion) }}
+
+  bazel-build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    needs:
+      - matrix-prep-bazelversion
+
+    # Run bazel test in each workspace with each version of Bazel supported
+    strategy:
+      fail-fast: false
+      matrix:
+        bazelversion: ${{ fromJSON(needs.matrix-prep-bazelversion.outputs.bazelversions) }}
+        folder:
+          - "."
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v3
+
+      # Cache build and external artifacts so that the next ci build is incremental.
+      # Because github action caches cannot be updated after a build, we need to
+      # store the contents of each build in a unique cache key, then fall back to loading
+      # it on the next ci run. We use hashFiles(...) in the key and restore-keys- with
+      # the prefix to load the most recent cache for the branch on a cache miss. You
+      # should customize the contents of hashFiles to capture any bazel input sources,
+      # although this doesn't need to be perfect. If none of the input sources change
+      # then a cache hit will load an existing cache and bazel won't have to do any work.
+      # In the case of a cache miss, you want the fallback cache to contain most of the
+      # previously built artifacts to minimize build time. The more precise you are with
+      # hashFiles sources the less work bazel will have to do.
+      - name: Mount bazel caches
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cache/bazel
+            ~/.cache/bazel-repo
+          key: bazel-cache-${{ hashFiles('**/BUILD.bazel', '**/*.bzl', 'WORKSPACE') }}
+          restore-keys: bazel-cache-
+
+      - name: Configure Bazel version
+        working-directory: ${{ matrix.folder }}
+        run: echo "${{ matrix.bazelversion }}" > .bazelversion
+
+      - name: bazel build //generator/...
+        env:
+          # Bazelisk will download bazel to here, ensure it is cached between runs.
+          XDG_CACHE_HOME: ~/.cache/bazel-repo
+        working-directory: ${{ matrix.folder }}
+        run: bazel --bazelrc=$GITHUB_WORKSPACE/.github/workflows/ci.bazelrc --bazelrc=.github/workflows/ci.bazelrc build //generator/...