cmd/go: "cannot find module golang.org/x/sys/unix" when GOOS=illumos

[jclulow]

I believe that the fix for #30888, applicable for GOOS=android, needs to cover the equivalence between the illumos and solaris in the same manner. It appears I missed this when adding the illumos build tag in #20603.

I built the latest master revision to make sure this is still an issue:

go version devel +2165452a37 Fri May 31 11:26:23 2019 +0000 illumos/amd64

(I get the "cannot find module golang.org/x/sys/unix" for an illumos/amd64 toolchain but not for a solaris/amd64 toolchain)

[jclulow]

(I'm looking into this.)

[jclulow]

In addition to the original fix for cross building for Android, it seems we need to amend the tags map constructed in cmd/go/internal/imports/tags.go. This probably also needs to happen for linux/android as well. I suspect it wasn't noticed there because people perhaps don't generally run a native Android toolchain?

[gopherbot]

Change https://golang.org/cl/179817 mentions this issue: cmd/go: recognise illumos suffix when constructing build list

[gopherbot]

Change https://golang.org/cl/179997 mentions this issue: cmd/go/internal/imports: match solaris files for illumos