try to get heap dumps if leak tests go out of memory again.

diff --git a/releng/build-scripts/build/test.xml b/releng/build-scripts/build/test.xml
index 97b723a..b5597d9 100644
--- a/releng/build-scripts/build/test.xml
+++ b/releng/build-scripts/build/test.xml
@@ -59,7 +59,7 @@
 	>

 		<ant antfile="plugins/${testPlugin}/test.xml" dir="${test.eclipseDir}">

 			<property name="eclipse-home" value="${test.eclipseDir}" />

-            <property name="extraVMargs" value="-XX:MaxPermSize=320m"/>

+            <property name="extraVMargs" value="-XX:MaxPermSize=320m -XX:+HeapDumpOnOutOfMemoryError"/>

 		</ant>

 	</target>