Fix macos linking errors by forcing use of clang.

PiperOrigin-RevId: 886465318

Author: iindyk

grain/oss/build_whl.sh

@@ -21,12 +21,17 @@ main() {
   # Enable host OS specific configs. For instance, "build:linux" will be used
   # automatically when building on Linux.
   write_to_bazelrc "build --enable_platform_specific_config"
+  write_to_bazelrc "build --verbose_failures"
   # Bazel 7.0.0 no longer supports dynamic symbol lookup on macOS. To resolve
   # undefined symbol errors in macOS arm64 builds, explicitly add the necessary
   # linker flags until dependencies are well defined. See
   # https://github.com/bazelbuild/bazel/issues/19730.
   write_to_bazelrc "build:macos --linkopt=-Wl,-undefined,dynamic_lookup"
   write_to_bazelrc "build:macos --host_linkopt=-Wl,-undefined,dynamic_lookup"
+  # Force clang on macos. Otherwise we get linker errors described in
+  # https://github.com/bazelbuild/bazel/issues/20838.
+  write_to_bazelrc "build:macos --action_env=CC=clang"
+  write_to_bazelrc "build:macos --action_env=CXX=clang++"
 
   write_to_bazelrc "build --@rules_python//python/config_settings:python_version=${PYTHON_VERSION}"
   # Set platform-wise file extension for extension modules.