fix freeze with -j and sync targets

moonbuild/core/DAG.moon

@@ -123,7 +123,7 @@ class DepNode
 				return false
 		for file in *@ins
 			if not exists file
-				error "Node #{name} has ran all of its parents, but can't run since #{file} doesn't exist"
+				error "Node #{@name} has ran all of its parents, but can't run since #{file} doesn't exist. Did you mean to use after instead of depends?"
 		return true
 
 	build: (opts={}) =>

moonbuild/core/multiprocessexecutor.moon

@@ -39,7 +39,7 @@ class Executor
 	addprocess: (node, opts) =>
 		if node.sync
 			while @nprocesses != 0
-				@waitprocess
+				@waitprocess!
 			node\build opts
 			node.built = true
 			node\updatecache!