Fix build failure on macOS for developers who have multiple clang installations

[ssaakaash]

Problem

The webrtc-sys build script was using Command::new("clang") to discover compiler library paths. On a system with Homebrew's llvm package installed, this command could resolve to /usr/local/bin/clang instead of the required Xcode toolchain compiler.

This caused the script to pass incorrect library search paths to the linker, resulting in errors like:

ld: warning: search path '/usr/local/lib/clang/22/lib/darwin' not found
ld: library 'clang_rt.osx' not found

Solution

The fix is to change Command::new("clang") to Command::new("cc") within the configure_darwin_sysroot function in build.rs.

On macOS, cc is the system's default compiler alias and is guaranteed to respect the toolchain set by xcode-select. This ensures that even if other versions of clang are in the PATH, the build script will always get the correct search paths from the active Xcode toolchain.

This makes the build process more robust and resilient to variations in the user's local environment.

[CLAassistant]

All committers have signed the CLA.

[davidzhao]

it would appear this change would break the build script, could you take a look?

[ssaakaash]

Don't know why the tests failed in the workflow, it doesn't break the current build script.