[libc] [llvm] [libc] Provide an implementation of the 'stdint.h' header (PR #83353)

[Nick Desaulniers via llvm-commits]

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

Fixing https://github.com/llvm/llvm-project/issues/65694 requires that we do something about including system headers (such as <stdint.h>).

https://github.com/llvm/llvm-project/pull/83353