automation: Add back Golang builds

This change adds back builds using the Go toolchain, which can be
downloaded and run via `bazel run`. Obtaining the Go toolchain this way
saves us from having to install it on the self-hosted runners directly,
and keeps the toolchain used in sync with the one used by bazel
automatically.

The matrix builds are moved to using the Go toolchain, and building
using bazel is done only with Linux. The rationale is:
* building on all platforms is useful for test coverage, and need only
  be done using either build system, but not necessarily both
* third parties are more likely to build the project using the Go
  tooling
* we intend to ship bazel-built binaries, so we need at least one build
  using bazel to protect the release builds

Bug: CUS-345

.github/workflows/main.yml

@@ -16,7 +16,25 @@ env:
   OPAL_RPC_CREDENTIALS: ${{ secrets.OPAL_RPC_CREDENTIALS }}
 
 jobs:
-  test-matrix:
+  bazel-builder:
+    runs-on:
+      - self-hosted
+      - os=linux
+      - arch=x64
+      - os_distribution=debian
+      - os_version=12
+      - revision=d04e89854b3931f4aaced77aa3a2fcad5834b3a6
+    timeout-minutes: 10
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: run all tests
+        run: |
+          # TODO(CUS-345): Enable remote execution
+          bazel test --config=noninteractive //...
+
+  golang-builder:
     runs-on:
       - self-hosted
       - "os=${{ matrix.os }}"
@@ -50,7 +68,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Test with Bazel
+      - name: build all
         run: |
           # TODO(CUS-345): Enable remote execution
-          bazel test --config=noninteractive //...
+          bazel run --config=noninteractive @rules_go//go -- build ./...
+
+      - name: run all tests
+        run: |
+          # TODO(CUS-345): Enable remote execution
+          bazel run --config=noninteractive @rules_go//go -- test ./...

.github/workflows/presubmit.yml

@@ -18,7 +18,25 @@ env:
   OPAL_RPC_CREDENTIALS: ${{ secrets.OPAL_RPC_CREDENTIALS }}
 
 jobs:
-  test-matrix:
+  bazel-builder:
+    runs-on:
+      - self-hosted
+      - os=linux
+      - arch=x64
+      - os_distribution=debian
+      - os_version=12
+      - revision=d04e89854b3931f4aaced77aa3a2fcad5834b3a6
+    timeout-minutes: 10
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: run all tests
+        run: |
+          # TODO(CUS-345): Enable remote execution
+          bazel test --config=noninteractive //...
+
+  golang-builder:
     runs-on:
       - self-hosted
       - "os=${{ matrix.os }}"
@@ -52,7 +70,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Test with Bazel
+      - name: build all
         run: |
           # TODO(CUS-345): Enable remote execution
-          bazel test --config=noninteractive //...
+          bazel run --config=noninteractive @rules_go//go -- build ./...
+
+      - name: run all tests
+        run: |
+          # TODO(CUS-345): Enable remote execution
+          bazel run --config=noninteractive @rules_go//go -- test ./...