x/sys/unix: dup2 syscall is missing on mips64*

[jcowgill]

What version of Go are you using (go version)?

go version go1.8.1 linux/mips64le

What operating system and processor architecture are you using?

Debian Stretch mips64el

What did you do?

Run x/sys/unix testsuite.

What did you expect to see?

It passes

What did you see instead?

# golang.org/x/sys/unix_test
./syscall_unix_test.go:326: undefined: unix.Dup2
FAIL    golang.org/x/sys/unix [build failed]

It appears the Dup2 syscall is missing on mips64 and mips64le.

[gopherbot]

CL https://golang.org/cl/43430 mentions this issue.

[binarycrusader]

So why is it ok that Dup2 was missing on mips64 and therefore added, but we aren't able to add it for Solaris as seen in #17042?

[jcowgill]

Didn't you add it here? golang/sys@68a71b6

[ianlancetaylor]

#17042 was originally opened for the syscall package (the topic line was changed later), and we said that we shouldn't add a new function to the syscall package. This issue is about the x/sys/unix package.

[binarycrusader]

Yes, sorry, I missed that subtlety.