[Bug go/69966] libgo: Port syscall.SetsockoptUcred from golang

[doko at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69966

Matthias Klose <doko at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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   Target Milestone|---                         |6.0