build: improve caching. (proxy-wasm#210)

There is a lot of unnecessary data in Bazel's cache, so this commit
removes Bazel's repository cache (~700 MiB), install base (150 MiB)
and tarballs from the Rust toolchain (350 MiB) before saving cache.

This decreases the cache size for each OS+runtime combination from
1.8 GiB to 700 MiB, which means that we can save cache from 2 runs
with 7 combinations using GitHub's 10 GiB total storage.

Additionally, Wasmtime builds so fast that we can disable cache to
free 2 slots for future OS+runtime combinations.

While there, fix caching on macOS, which uses a different location.

Signed-off-by: Piotr Sikora <[email protected]>

Author: PiotrSikora

.github/workflows/cpp.yml

@@ -99,12 +99,13 @@ jobs:
       if: startsWith(matrix.os, 'macos')
       run: brew install ninja
 
-    - name: Mount Bazel cache
+    - name: Bazel cache
+      if: matrix.runtime != 'wasmtime'
       uses: actions/cache@v2
       with:
         path: |
           ~/.cache/bazel
-          ~/.cache/bazelisk
+          /private/var/tmp/_bazel_runner/
         key: bazel-${{ matrix.os }}-${{ matrix.runtime }}-${{ hashFiles('WORKSPACE', '.bazelrc', '.bazelversion', 'bazel/cargo/Cargo.raze.lock', 'bazel/dependencies.bzl', 'bazel/repositories.bzl') }}
 
     - name: Test
@@ -114,3 +115,27 @@ jobs:
     - name: Test (signed Wasm module)
       run: |
         bazel test --test_output=errors --define runtime=${{ matrix.runtime }} --per_file_copt=src/signature_util.cc,test/signature_util_test.cc@-DPROXY_WASM_VERIFY_WITH_ED25519_PUBKEY=\"$(xxd -p -c 256 test/test_data/signature_key1.pub | cut -b9-)\" //test:signature_util_test
+
+    - name: Cleanup Bazel cache
+      if: matrix.runtime != 'wasmtime'
+      run: |
+        export OUTPUT=$(bazel info output_base)
+        # BoringSSL's test data (90 MiB).
+        rm -rf ${OUTPUT}/external/boringssl/crypto_test_data.cc
+        rm -rf ${OUTPUT}/external/boringssl/src/crypto/*/test/
+        rm -rf ${OUTPUT}/external/boringssl/src/third_party/wycheproof_testvectors/
+        # LLVM's tests (500 MiB).
+        rm -rf ${OUTPUT}/external/llvm*/test/
+        # V8's tests (100 MiB).
+        if [ -d "${OUTPUT}/external/v8/test/torque" ]; then
+          mv ${OUTPUT}/external/v8/test/torque ${OUTPUT}/external/v8/test_torque
+          rm -rf ${OUTPUT}/external/v8/test/*
+          mv ${OUTPUT}/external/v8/test_torque ${OUTPUT}/external/v8/test/torque
+        fi
+        # Unnecessary CMake tools (65 MiB).
+        rm -rf ${OUTPUT}/external/cmake-*/bin/{ccmake,cmake-gui,cpack,ctest}
+        # Distfiles for Rust toolchains (350 MiB).
+        rm -rf ${OUTPUT}/external/rust_*/*.tar.gz
+        # Bazel's repository cache (650-800 MiB) and install base (155 MiB).
+        rm -rf $(bazel info repository_cache)
+        rm -rf $(bazel info install_base)