Bug 531553 - Make MissingBuilder use null schedulingRule

As missingBuilder does nothing, no reason to assign in the default
workspaceroot schedulingrule.

Change-Id: I37632e4bb4891829c0bbfdc89222da3073adc8cb
Signed-off-by: Mickael Istria <mistria@redhat.com>
diff --git a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/events/BuildManager.java b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/events/BuildManager.java
index 9d90df5..7c6ed40 100644
--- a/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/events/BuildManager.java
+++ b/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/events/BuildManager.java
@@ -98,6 +98,11 @@
 			return name;
 		}
 
+		@Override
+		public ISchedulingRule getRule(int kind, Map<String, String> args) {
+			return null;
+		}
+
 	}
 
 	private static final int TOTAL_BUILD_WORK = Policy.totalWork * 1000;