[dev.cmdgo] cmd/go: remove modload.ModRoot function
In some cases, ModRoot was being called in a multi module context. In
those cases, pass in the correct main module. In other cases, a
mainModule variable was already available, so call MainModules.ModRoot
on that mainModule variable to make it more clear. In yet other cases
ModRoot is just needed to determine GoMod, so determine modroot from
the current directory in those cases.
For #45713
Change-Id: I8c8aa633cfae40d0c8740bdbf985f2b60c9daf2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/339171
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>