[Bug libstdc++/126786] [libstdc++] Module fallback installs empty interface files but the manifest lists them

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126786

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The fallback should never be used, it only exists to avoid breaking bootstrap
for targets where nobody is testing/using the std modules. If the fallback is
being used, then that's the bug and that should be fixed.