[clang] [clang][ASTImporter] Not using primary context in lookup table (PR #118466)

[Balázs Kéri via cfe-commits]

balazske wrote:

I have tested the change with CTU analysis and did not see significant difference, and no new crashes (in these tests there was one known instance of unreachable at ASTImporterLookupTable.cpp:121 that is fixed by the change). There were some differences in the found reports, probably explored paths are different.

https://github.com/llvm/llvm-project/pull/118466