[Bug c/40989] -Werror= and #pragma diagnostics do not work with group flags

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40989
Bug 40989 depends on bug 53063, which changed state.

Bug 53063 Summary: encode group options in the .opt files
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53063

           What    |Removed                     |Added
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             Status|WAITING                     |RESOLVED
         Resolution|---                         |FIXED