[clang] [C++] Expose nullptr_t from stddef.h in C++ mode (PR #154599)

[Aiden Grossman via cfe-commits]

boomanaiden154 wrote:

I'm pretty sure the libc++ failure is related. We're getting consistent failures on the premerge buildbot after this change landed:

1. https://lab.llvm.org/staging/#/builders/192/builds/1329
2. https://lab.llvm.org/staging/#/builders/192/builds/1330

https://github.com/llvm/llvm-project/pull/154599