LC0 compilation BUG on macOS

[Chess321]

Linker Error: Undefined symbols (libc++) when compiling gtest on macOS arm64 (Homebrew LLVM)

I am encountering a linker failure when compiling version lc0-0.32.0 on an Apple Silicon. The issue appears to be related to the C++ standard library (libc++) not being correctly linked.

This exact build process was successful with previous versions of the compiler and build system on the same machine. I suspect that a recent update to Homebrew LLVM or the Meson/Ninja build tools might have altered how linker flags are passed.

🐛 Error Description

The build fails during the linking stage of the googletest subproject because symbols from the C++ standard library cannot be found.

Relevant Snippet from the Build Log:

[122/325] Linking target subprojects/g...st-1.15.2/googletest/libgtest-all.dyli
FAILED: [code=1] subprojects/googletest-1.15.2/googletest/libgtest-all.dylib 

# The linker command shows the use of Homebrew Clang and the -nostdinc++ flag
/opt/homebrew/opt/llvm/bin/clang++  -o subprojects/googletest-1.15.2/googletest/libgtest-all.dylib [...] -nostdinc++

# The missing symbols belong to libc++ (std::__1)
Undefined symbols for architecture arm64:
  "std::__1::__hash_memory(void const*, unsigned long)", referenced from:
      testing::internal::(anonymous namespace)::UnitTestFilter::UnitTestFilter(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&) in lto.o
      # ... further std::__1:: symbols
ld: symbol(s) not found for architecture arm64
clang++: error: linker command failed with exit code 1 (use -v to see invocation)


OS:	macOS 26.1 25B78 arm64
Host:	MacBook Pro M1 Max
Compiler (C++):	/opt/homebrew/opt/llvm/bin/clang++ (Homebrew clang version 21.1.5)
Shell:	/bin/zsh 5.9
Build System:	Meson 1.9.1 / Ninja 1.13.1
lc0 Version:	0.32.0

[borg323]

When build tools change or sometimes even when the os updates, you sometimes have to delete the build directory.