CMake 4 no longer sets the CMAKE_OSX_SYSROOT variable by default, causing the
lldb build to fail after all GitHub-hosted runners have been upgraded to
CMake 4.
As a workaround, the variable is set using CMake command line options. There
is a PR to fix this issue in the llvm-project:
https://github.com/llvm/llvm-project/pull/138020. We might want to remove
this workaround after that PR has been merged.
5c7f64bcc0