[clang] [clang][modules] Allow module maps with textual headers to be non-affecting (PR #89441)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

@sam-mccall That makes sense.

I think one option we have here is to consider all module maps describing a textual header that got included as affecting. I'm concerned that a long chain of textual header includes might again be problematic.

For this particular test, we only need to consider the module maps describing `use`d modules affecting to keep `-fmodules-strict-decluse` happy, which seems like a more precise solution.

https://github.com/llvm/llvm-project/pull/89441