[clang] [clang][SourceManager] Use `getFileLoc` when computing `getPresumedLoc` (PR #166255)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

@SergejSalnikov if you have a fix handy for the CI failure, I can prioritize reviewing it ASAP. Otherwise, I can revert this commit to give you more time to work on a fix. Let me know which you prefer.

https://github.com/llvm/llvm-project/pull/166255