cmd/go: cannot find package when importing dependencies with the unix build constraint [1.19 backport] #54736
Description
@bcmills requested issue #54712 to be considered for backport to the next 1.19 minor release.
@gopherbot, please backport to Go 1.19. This is a subtle bug in a feature introduced in Go 1.19, and the fix in Go 1.20 will mask spurious build failures that users on Go 1.19 will run into.