[clang] [clang][modules] Print library module manifest path. (PR #76451)

[Boris Kolpackov via cfe-commits]

boris-kolpackov wrote:

If I understand correctly, this invents a new option just to print the std modules path. Is there a reason why we cannot just print this information as part of `-print-search-dirs`? The benefit of this will be saving an extra compiler invocation in case the build system already uses this option, for example, to extract the library search paths (`build2` does this). BTW, this would also allow you to sidestep the whole "what to print if there is no path" issue -- just omit the entry from the output.

If for some reason a separate option is desirable, can we then also print this information as part of `-print-search-dirs`?

https://github.com/llvm/llvm-project/pull/76451