[clang] [clang] Expose CrossTU context in CheckerContext.h (PR #181713)

[Balázs Benics via cfe-commits]

steakhal wrote:

I see what you want. I'm strongly against doing this.
Exposing this would allow to fill the CTU context cache. And if we didn't have limits on the size of that cache, it would blow up by recursively merging all TUs making effectively a unity build.

This sort of crosstalk (side effect) of filling the CTU cache would likely mean that the use case of inlining remote calls would not get cache slots.

I think what you really want here is a proper cross translation unit analysis that doesn't use the unreliable ASTImporter and scales well for many translation units. This should be covered by [SSAF](https://discourse.llvm.org/t/rfc-scalable-static-analysis-framework/88678) in the upcoming months.

cc @NagyDonat 

https://github.com/llvm/llvm-project/pull/181713