[libcxx-commits] [libcxx] [RFC][libc++] Install modules. (PR #75741)

[Mark de Wever via libcxx-commits]

mordante wrote:

> Also, I don't think we need the include directories in the metadata.
> 
> The `local-arguments` are meant to cover things that are only needed when translating the module sources, but not needed when translating something that imports the module.
> 
> The paths to the standard library headers are part of the "basic toolchain configuration arguments" and must match across both the BMI and the TU performing the import.
> 
> Please see [P2581R2](https://wg21.link/P2581R2) for an extended discussion of that problem.

In libc++ the `std` module has parts of its implementation in `<header>.inc` files. These should be included during the building of the module. Typically compilers will look in the path of the .cpp file, but I feel it's better to do that explicitly. This is not the path of the standard library header files. I indeed expect compiler to find that path.

https://github.com/llvm/llvm-project/pull/75741