CI: add --sandbox_debug --verbose_failures to Bazel builds for debugging

Author: mjp41

.github/workflows/main.yml

@@ -154,9 +154,10 @@ jobs:
       uses: actions/cache@v4
       with:
         path: "~/.cache/bazel"
-        key: bazel-${{ matrix.os }}-${{ matrix.build-type }}
-    - run: bazel build -c opt //:snmalloc
-    - run: bazel build -c opt //:snmalloc-rs
+        key: bazel-v2-${{ matrix.os }}-${{ matrix.build-type }}
+    - run: bazel clean --expunge
+    - run: bazel build -c opt --sandbox_debug --verbose_failures //:snmalloc 2>&1 || (cat $(bazel info output_base)/external/rules_foreign_cc*/*/build_log 2>/dev/null; false)
+    - run: bazel build -c opt --sandbox_debug --verbose_failures //:snmalloc-rs
     - run: bazel test -c opt --config=asan //fuzzing:snmalloc_fuzzer
       if: ${{ matrix.os != 'macos-14' && matrix.os != 'macos-15' }}