Releng: use previous SDK for installing the previous compiler into

- remove original jdt.core also from baseLocation
diff --git a/releng/build-scripts/build/run.xml b/releng/build-scripts/build/run.xml
index 74b016d..5e1274e 100644
--- a/releng/build-scripts/build/run.xml
+++ b/releng/build-scripts/build/run.xml
@@ -241,6 +241,7 @@
         </ant>
 		<delete>
 		    <fileset dir="${bootLocation}/plugins/" includes="org.eclipse.jdt.core_*.v* org.eclipse.jdt.core.source_*.v*" />
+		    <fileset dir="${baseLocation}/plugins/" includes="org.eclipse.jdt.core_*.v* org.eclipse.jdt.core.source_*.v*" />
 		</delete>
     </target>