ci: stabilize Windows Bazel PATH inputs

.bazelrc

@@ -29,6 +29,9 @@ common:linux --test_env=PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
 common:macos --test_env=PATH=/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
 
 # Pass through some env vars Windows needs to use powershell?
+# CI overrides PATH in `.github/scripts/run-bazel-ci.sh` with a cache-stable
+# allow-list so unrelated GitHub Windows image tool updates do not invalidate
+# BuildBuddy action/test cache entries.
 common:windows --test_env=PATH
 common:windows --test_env=SYSTEMROOT
 common:windows --test_env=COMSPEC

.github/scripts/run-bazel-ci.sh

@@ -306,7 +306,6 @@ if [[ "${RUNNER_OS:-}" == "Windows" ]]; then
     INCLUDE
     LIB
     LIBPATH
-    PATH
     UCRTVersion
     UniversalCRTSdkDir
     VCINSTALLDIR
@@ -323,6 +322,42 @@ if [[ "${RUNNER_OS:-}" == "Windows" ]]; then
       post_config_bazel_args+=("--action_env=${env_var}" "--host_action_env=${env_var}")
     fi
   done
+
+  # The GitHub Windows image puts many unrelated versioned tools on PATH. Those
+  # entries are still part of Bazel action/test keys when PATH is forwarded, so
+  # image churn such as Maven minor-version updates can invalidate otherwise
+  # reusable cache entries. Keep only the PATH segments Bazel actions/tests need.
+  windows_cache_stable_path_entries=()
+  if [[ -n "${PATH:-}" ]]; then
+    IFS=';' read -r -a windows_path_entries <<< "${PATH}"
+    for path_entry in "${windows_path_entries[@]}"; do
+      case "${path_entry}" in
+        *'Microsoft Visual Studio'* | \
+          *'Windows Kits'* | \
+          *'Microsoft SDKs'* | \
+          'C:\Program Files\Git\'* | \
+          'C:\Program Files\PowerShell\'* | \
+          'C:\Users\runneradmin\AppData\Local\Microsoft\WindowsApps' | \
+          'C:\hostedtoolcache\windows\node\'* | \
+          'C:\Windows' | \
+          'C:\Windows\'* | \
+          'D:\a\_temp\install-dotslash\bin')
+          windows_cache_stable_path_entries+=("${path_entry}")
+          ;;
+      esac
+    done
+  fi
+
+  if (( ${#windows_cache_stable_path_entries[@]} > 0 )); then
+    stable_windows_path="$(IFS=';'; printf '%s' "${windows_cache_stable_path_entries[*]}")"
+    post_config_bazel_args+=(
+      "--action_env=PATH=${stable_windows_path}"
+      "--host_action_env=PATH=${stable_windows_path}"
+      "--test_env=PATH=${stable_windows_path}"
+    )
+  elif [[ -n "${PATH:-}" ]]; then
+    post_config_bazel_args+=("--action_env=PATH" "--host_action_env=PATH" "--test_env=PATH")
+  fi
 fi
 
 bazel_console_log="$(mktemp)"