[libc-commits] [libc] [libc] Acquire the lock for scanf files (PR #67357)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 approved this pull request.

LG. I'm guessing there's not a good way to check if `ungetc_unlocked` is available. The GPU case will probably be ismilar to `USE_SYSTEM_FILE` so I'm assuming that won't cause any issues.

https://github.com/llvm/llvm-project/pull/67357