[Bug target/97250] Implement -march=x86-64-v2, -march=x86-64-v3, -march=x86-64-v4 for x86-64

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97250

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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   Last reconfirmed|                            |2020-09-30
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1