[Bug libstdc++/66530] libstdc++ testsuite links to incorrect shared libstdc++ library

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66530

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Created attachment 35788
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35788&action=edit
Set PATH for all testsuites not just for libstdc++

Since the problem isn't specific to libstdc++ we should fix it globally for all
target libs.