[clang] [clang] Make verbose output streams configurable for embedded clients (PR #226022)

[Anutosh Bhat via cfe-commits]

anutosh491 wrote:

> Not sure I follow.

Oops sorry. My wording made it sound more complicated 😅 
We were talking about different things when I mentioned concurrency. I only meant that selecting the destination would be process-wide, not that the stream itself has different concurrency issues.

https://github.com/llvm/llvm-project/pull/226022