[clang] [clang][modules] Remove preloaded SLocEntries from PCM files (PR #66962)

[Ben Langmuir via cfe-commits]

benlangmuir wrote:

> I changed SourceManager::isInTheSameTranslationUnit() to check for that case explicitly instead of relying on the fact/bug that built-ins buffers happened to be assigned an untranslated include SourceLocation.

What is the translated location you get here?  It's hard for me to tell if the comment in `isBeforeInTranslationUnit` is describing the desired behaviour or just a consequence of how it happened to work at the time.

https://github.com/llvm/llvm-project/pull/66962