[clang] Reland Print library module manifest path again (PR #84881)

[Mark de Wever via cfe-commits]

mordante wrote:

> > > > The file we're looking for is `modules.json`; Renaming it `libc++.modules.json` like `.so` / `.a` file might be a better idea which could avoid name clashes when installed in `/usr/lib`.
> > > 
> > > 
> > > but i didn't rename it, it was with the libc++ prefix directly :/
> > 
> > 
> > Good point I did :-/ It seems we originally talked about `modules.json` and later mentioned using the libname. @ChuanqiXu9 I prefer to keep the current name `libc++.modules.json` and adjust clang. WDYT?
> 
> Could you elaborate the reason more? I feel like renaming `libc++.modules.json` to `modules.json` is straightforward. Maybe I didn't take part it in the old disscussion or I missed : )

It would allow to install libstdc++ and libc++ in the same lib directory without "fighting" who owns `modules.json`. Also if we want to provide `libc++-asan.so` in the future we can provide `libc++-asan.modules.json`. Whether we need a different `module.json` for ASan is unknown at the moment, but I can imagine we have additional compiler or linker flags for ASan. 

https://github.com/llvm/llvm-project/pull/84881