[clang] [clang][analyzer] Forward CTU-import failure conditions (PR #189064)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

By the way I checked that the load threshold reached diagnostic (which has "remark" severity) does not appear in the PLIST output. (I copied and tweaked the RUN lines of `load-threshold.cpp` and used `-Rctu` to ensure that the remark is emitted. The remark did appear on the standard output printout, but has no trace in the PLIST file.)

This is probably a good thing for now (because this way we won't affect software that consumes the PLIST), but on a longer term we might want to also expose this information through PLIST as well.

https://github.com/llvm/llvm-project/pull/189064