Merge component 'engine' from git@github.com:docker/engine master

components/engine/hack/make.ps1

@@ -130,7 +130,7 @@ Function Check-InContainer() {
 # outside of a container where it may be out of date with master.
 Function Verify-GoVersion() {
     Try {
-        $goVersionDockerfile=(Get-Content ".\Dockerfile" | Select-String "ENV GO_VERSION").ToString().Split(" ")[2]
+        $goVersionDockerfile=(Select-String -Path ".\Dockerfile" -Pattern "^FROM golang:").ToString().Split(" ")[1].SubString(7)
         $goVersionInstalled=(go version).ToString().Split(" ")[2].SubString(2)
     }
     Catch [Exception] {