macOS arm64 build fails: mongo-c-driver's lld-linker TRY_COMPILE probe rejected by Xcode clang

[rustyconover]

Summary

While building this extension as part of the DuckDB community extensions program (via the haybarn-community-extensions fork's CI), the macOS arm64 build fails. It's not your extension's own C++ code — it's the vcpkg-managed mongo-c-driver dependency's build-time linker probe — but flagging it here since it blocks your macOS build and you control the pinned mongo-c-driver version.

Error

CMake Error at src/libmongoc/CMakeLists.txt:453 (TRY_COMPILE):
  Failed to configure test project build system.
...
/usr/bin/cc -fPIC -fuse-ld=lld -arch arm64 -mmacosx-version-min=11.0 ... -o cmTC_cb38d
clang: error: invalid linker name in argument '-fuse-ld=lld'
ninja: build stopped: subcommand failed.

error: building mongo-c-driver:arm64-osx-release failed with: BUILD_FAILED

Full failing job: https://github.com/Query-farm-haybarn/haybarn-community-extensions/actions/runs/33027261113 (MacOS osx_arm64 leg; Linux and Windows build fine)

Root cause

mongo-c-driver's own CMake (src/libmongoc/CMakeLists.txt:453) does a TRY_COMPILE to detect lld-linker support by passing -fuse-ld=lld to the host compiler. On this runner, that resolves to Apple's Xcode clang, which doesn't recognize the bare lld linker name (Apple's clang only accepts a handful of built-in linker names; a real lld binary isn't on PATH/wired up the way it is on Linux). The TRY_COMPILE fails outright, which cascades into "Failed to configure test project build system" and aborts the whole mongo-c-driver vcpkg build before it even gets to compiling.

Since mongo-c-driver version is pinned via this extension's vcpkg.json/vcpkg_commit, a version bump (or a vcpkg overlay port patch) is the practical lever here even though the bug itself lives upstream in mongo-c-driver.

Suggested fix

• Check if a newer mongo-c-driver release has fixed/removed this lld-detection TRY_COMPILE for macOS, and bump the pinned version if so, or
• Add a small vcpkg portfile patch/overlay that skips the lld probe (or passes a linker name Xcode's clang actually understands) on osx triplets.

Thanks for maintaining this extension — happy to help verify a fix if useful!