TEMPORARY! Avoid compilation errors in nocs on darwin

it is now possible to create Spec structs on darwin machines. This may
be superseded by opencontainers#135

This is primarily used by https://github.com/cloudfoundry-incubator/nocs
[#101501242] at https://www.pivotaltracker.com/n/projects/1158420

Signed-off-by: Gareth Smith <gsmith@pivotal.io>

config_darwin.go

@@ -0,0 +1,14 @@
+// +build darwin
+
+package specs
+
+// User specifies specific user and group information for the container's
+// main process.
+type User struct {
+	// UID is the user id.
+	UID int32 `json:"uid"`
+	// GID is the group id.
+	GID int32 `json:"gid"`
+	// AdditionalGids are additional group ids set for the container's process.
+	AdditionalGids []int32 `json:"additionalGids"`
+}