ci: get Bazel's output paths from within Docker. (proxy-wasm#250)

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

Author: PiotrSikora

.github/workflows/cpp.yml

@@ -253,7 +253,9 @@ jobs:
     - name: Cleanup Bazel cache
       if: ${{ github.ref == 'refs/heads/master' && (matrix.runtime != 'wasmtime' || startsWith(matrix.run_under, 'docker')) }}
       run: |
-        export OUTPUT=$(bazel info output_base)
+        export OUTPUT=$(${{ matrix.run_under }} bazel info output_base)
+        echo "===== BEFORE ====="
+        du -s ${OUTPUT}/external/* $(dirname ${OUTPUT})/* | sort -rn | head -20
         # BoringSSL's test data (90 MiB).
         rm -rf ${OUTPUT}/external/boringssl/crypto_test_data.cc
         rm -rf ${OUTPUT}/external/boringssl/src/crypto/*/test/
@@ -271,5 +273,7 @@ jobs:
         # 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)
+        rm -rf ${OUTPUT}/../cache
+        rm -rf ${OUTPUT}/../install
+        echo "===== AFTER ====="
+        du -s ${OUTPUT}/external/* $(dirname ${OUTPUT})/* | sort -rn | head -20