engine: resources: Add nodocker build tag

Make it easy to disable building docker which is enormous.

engine/resources/docker_container.go

@@ -15,6 +15,8 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+// +build !nodocker
+
 package resources
 
 import (

engine/resources/docker_container_test.go

@@ -15,6 +15,8 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+// +build !nodocker
+
 package resources
 
 import (