🌩️ Use cloud caching (#14)

No need to use GitHub's action cache.

The credentials used here are intended to be used by third parties. That
is, they're safe to have in this workflow and may be copy-pasted into
any projects that would like to use NativeLink as remote cache.

.github/workflows/test-stdlib.yaml

@@ -7,7 +7,6 @@ name: 🔥 Test Mojo Standard library
   pull_request:
     branches: [main]
 
-permissions: read-all
 
 jobs:
   stdlib-tests:
@@ -18,8 +17,21 @@ jobs:
         os: [ubuntu-24.04]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
+    permissions:
+      id-token: write
     steps:
 
+      - name: Get Web Identity Token via Cognito Identity Pool
+        id: web_id_token
+        # See: https://github.com/catnekaise/cognito-idpool-auth/issues/6
+        uses: >- # alpha
+          catnekaise/cognito-idpool-basic-auth@287d4dabb527d8b78d3df6e0436d46e3abd209d3
+        with:
+          # yamllint disable rule:line-length
+          cognito-identity-pool-id: "us-east-2:7edef192-7c1c-4e55-8ab4-6035b9c2288f"
+          aws-account-id: "471112781046"
+          aws-region: "us-east-2"
+          audience: "sts.amazonaws.com"
       - name: Checkout
         uses: >- #v4.1.6
           actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29
@@ -31,25 +43,24 @@ jobs:
       - name: Cache Nix derivations
         uses: >- # v6
           DeterminateSystems/magic-nix-cache-action@87e8236f46702ab0ce5a058b605a173ec88d618e
-      - name: Mount bazel cache
-        uses: >- # v4.0.2
-          actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9
-        with:
-          path: |
-            ~/.cache/bazel
-          key: >-
-            ${{ runner.os }}-bazel-${{ hashFiles(
-              '.bazelversion',
-              '.bazelrc',
-              'MODULE.bazel',
-              'MODULE.bazel.lock',
-              '**/*.nix',
-              'flake.lock'
-            ) }}
-          restore-keys: |
-            ${{ runner.os }}-bazel-
+
+#     - name: Create secret from token
+#       uses: actions/github-script@v6
+#       with:
+#         # yamllint disable rule:line-length
+#         script: >-
+#           core.setSecret('NATIVELINK_TOKEN',
+#           '${{ steps.web_id_token.outputs.cognito_identity_oidc_access_token }}')
 
       - name: Invoke Bazel build in Nix shell
+        env:
+          NATIVELINK_TOKEN: ${{ env.NATIVELINK_TOKEN }}
         run: |
           nix develop --impure --command \
-          bash -c "bazel test --jobs=4 @mojo//... --verbose_failures"
+          bash -c "bazel test \
+            --jobs=4 \
+            --verbose_failures \
+            --experimental_remote_cache_async \
+            --remote_header=x-nativelink-api-key=$NATIVELINK_TOKEN \
+            --remote_cache=grpcs://cas-gha-ci.build-faster.nativelink.net:443 \
+            @mojo//..."