bazel/toolchains/cc/mongo_apple/mongo_apple_toolchain.bzl declares LLVM_PATH in the mongo_apple_brew_llvm_toolchain_config repository rule's environ list, but _get_llvm_info() never reads it. The compiler prefix is always resolved through brew --prefix llvm@$LLVM_VERSION.

As a result the macOS toolchain can only be pointed at a Homebrew-managed LLVM whose formula matches the version pinned in .bazelrc. An LLVM installed elsewhere - for example the Xcode / CommandLineTools clang - cannot be selected, even though the environment variable to do so is already declared.

Proposed change: read LLVM_PATH in _get_llvm_info() and use it directly as the prefix when set, falling back to the existing brew --prefix lookup otherwise. Add a matching LLD_PATH for the lld prefix, which _get_lld_info() resolves separately via brew --prefix lld@$LLVM_VERSION.