[libc-commits] [libc] [libc] Move __LLVM_LIBC__ define to __llvm-libc-common.h (PR #126877)

[Petr Hosek via libc-commits]

petrhosek wrote:

This issue was raised by @ldionne in #125587. I believe that defining `__LLVM_LIBC__` in `__llvm-libc-common.h` is the simplest solution but I'm open to other suggestions.

https://github.com/llvm/llvm-project/pull/126877