[Bug libstdc++/119266] libstdc++.modules.json has wrong path

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119266

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I wonder if using std::filesystem (or std::experimental::filesystem for C++14)
would make this path handling more robust.