make package docker/pkg/platform support darwin

Signed-off-by: allencloud <allen.sun@daocloud.io>

pkg/platform/architecture_unix.go

@@ -1,5 +1,7 @@
-// +build freebsd solaris
+// +build freebsd solaris darwin
 
+// Package platform provides helper function to get the runtime architecture
+// for different platforms.
 package platform
 
 import (
@@ -7,7 +9,7 @@ import (
 	"strings"
 )
 
-// runtimeArchitecture get the name of the current architecture (i86pc, sun4v)
+// runtimeArchitecture gets the name of the current architecture (x86, x86_64, i86pc, sun4v, ...)
 func runtimeArchitecture() (string, error) {
 	cmd := exec.Command("/usr/bin/uname", "-m")
 	machine, err := cmd.Output()