[clang][deps] Handle modular dependencies present in PCH

Authored by jansvoboda11 on Jun 14 2021, 2:30 AM.


[clang][deps] Handle modular dependencies present in PCH

When a translation unit uses a PCH and imports the same modules as the PCH, we'd prefer to resolve to those modules instead of inventing new modules and reporting them as modular dependencies. Since the PCH modules have already been built nudge the compiler to reuse them when deciding whether to build a new module and don't report them as regular modular dependencies.

Depends on D103524 & D103802.

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D103526