[clang] [NFC] [clang] Use std::string instead of StringRef to reduce stack usage (PR #114285)

[Krzysztof Parzyszek via cfe-commits]

kparzysz wrote:

I was able to see the internal bug report.  This shows up when some code on Windows runs clang (via a library call), and it ends up crashing due to stack overflow.  The crash happens in this function, in "__chkstk" to be exact.

https://github.com/llvm/llvm-project/pull/114285