[libc-commits] [libc] [libc] [startup] add cmake function to merge separated crt1 objects (PR #75413)

[Schrodinger ZHU Yifan via libc-commits]

SchrodingerZhu wrote:

@jhuber6 unfortunately, `llvm_check_linker_flag` does not really work. However, `check_cxx_compiler_flag("-r" LIBC_LINKER_SUPPORTS_RELOCATABLE)` works fine.

https://github.com/llvm/llvm-project/pull/75413