[Bug libstdc++/29366] atomics config for sh is weird

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29366
Bug 29366 depends on bug 53579, which changed state.

Bug 53579 Summary: libstdc++ configure use CXXFLAGS instead of 
CXXFLAGS_FOR_TARGET
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53579

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE