The logic was incorrectly written from vfs/os.go. zipfs filesystem
passes actual paths during dirTree building. So we need to join the paths
to determine whether they are under GOROOT or GOPATH.
Updates golang/go#27205
Change-Id: Ic4330fce02c6ebfc44ae21122e2412c33f0cd45a
Reviewed-on: https://go-review.googlesource.com/138435
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
ae8529dc16