llvm-project

c1e78ed3 - Reland "[clang][modules-driver] Add support for C++ named modules and import std" (2nd attempt) (#194475)

Reland "[clang][modules-driver] Add support for C++ named modules and import std" (2nd attempt) (#194475) This reverts #193857 and relands #193312. This adds basic support for explicit C++ named module builds, managed natively by the Clang driver, including support for use of the Standard library modules. This follows #187606, which adds the same for Clang modules. Current limitations: - Standard library modules are still compiled to object files instead of using the provided shared library. (This will be addressed in a follow-up soon.) - Caching is not supported yet (but likely to be added during the upcoming GSoC cycle). - Importing C++ standard library modules into Clang modules is not supported (and not expected in the near term). RFC: https://discourse.llvm.org/t/rfc-modules-support-simple-c-20-modules-use-from-the-clang-driver-without-a-build-system