[libc-commits] [libc] [libc] Add unistd overlay (PR #119312)

[Tristan Ross via libc-commits]

RossComputerGuy wrote:

Oh fun, it fails CI and I don't know why:
```
 CMake Error at /home/runner/work/llvm-project/llvm-project/libc/cmake/modules/LLVMLibCObjectRules.cmake:172 (message):
  An entrypoint alias should have exactly one dependency.
Call Stack (most recent call first):
  /home/runner/work/llvm-project/llvm-project/libc/cmake/modules/LLVMLibCFlagRules.cmake:158 (create_entrypoint_object)
  /home/runner/work/llvm-project/llvm-project/libc/cmake/modules/LLVMLibCFlagRules.cmake:158 (cmake_language)
  /home/runner/work/llvm-project/llvm-project/libc/cmake/modules/LLVMLibCFlagRules.cmake:251 (expand_flags_for_target)
  /home/runner/work/llvm-project/llvm-project/libc/cmake/modules/LLVMLibCObjectRules.cmake:393 (add_target_with_flags)
  /home/runner/work/llvm-project/llvm-project/libc/src/unistd/CMakeLists.txt:65 (add_entrypoint_object)
```
Are all the ones I updated aliases?

https://github.com/llvm/llvm-project/pull/119312