Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?

go version devel +ebbe4f8 Wed May 18 21:20:33 2016 +0000 linux/amd64

1. What operating system and processor architecture are you using (go env)?

Irrelevant.

1. What did you do?

$ cat $GOPATH/src/vendor/bar/bar.go
package bar

var World = "world"
$ cat $GOPATH/src/foo/foo.go
package main

import (
    "fmt"

    "bar"
)

func main () {
    fmt.Println("Hello", bar.World)
}
$ go build -compiler gccgo foo

1. What did you expect to see?

Nothing, and an executable 'foo' created.

1. What did you see instead?

$ go build -compiler gccgo foo
# foo
src/foo/foo.go:6:5: error: import file ‘bar’ not found
  "bar"
     ^
src/foo/foo.go:10:23: error: reference to undefined name ‘bar’
  fmt.Println("Hello", bar.World)
                       ^

This isn't that serious as I mostly use gccgo for packaging purposes and most packages are not built with bundled dependencies, but it's caused one package build failure I know about (https://launchpad.net/ubuntu/+source/docker-registry/2.3.1~ds2-1/+build/9640391).