[Bug libstdc++/90770] Building with --enable-libstdcxx-debug and make profiledbootstrap fails with mv: cannot stat 'Makefile': No such file or directory

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90770

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk only for now.