Fix cross compile non cgo and linux systems

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Upstream-commit: 7a8ea91392e0cc97caf2a6edc3b262b33a5b446d
Component: engine

components/engine/daemon/execdriver/native/create.go

@@ -1,4 +1,4 @@
-// +build linux
+// +build linux,cgo
 
 package native
 

components/engine/daemon/execdriver/native/driver.go

@@ -1,4 +1,4 @@
-// +build linux
+// +build linux,cgo
 
 package native
 

components/engine/daemon/execdriver/native/driver_unsupported_nocgo.go

@@ -0,0 +1,13 @@
+// +build linux,!cgo
+
+package native
+
+import (
+	"fmt"
+
+	"github.com/dotcloud/docker/daemon/execdriver"
+)
+
+func NewDriver(root, initPath string) (execdriver.Driver, error) {
+	return nil, fmt.Errorf("native driver not supported on non-linux")
+}

components/engine/daemon/execdriver/native/info.go

@@ -1,4 +1,4 @@
-// +build linux
+// +build linux,cgo
 
 package native