[clang] [libc] Fix wrapper headers if std=c99 is set (PR #168386)

[Dominik Adamski via cfe-commits]

DominikAdamski wrote:

> Why does this cause errors? I figured redeclarations of externs was legal. Maybe the attributes?

The problem relates to different declarations of the stdio functions if std=c99 is set.

https://github.com/llvm/llvm-project/pull/168386