SLING-9984 fix locale specific tests on Java >= 9
diff --git a/pom.xml b/pom.xml
index 9976d78..d077583 100644
--- a/pom.xml
+++ b/pom.xml
@@ -190,6 +190,8 @@
                             <controlPort>${sling.control.port}</controlPort>
                             <runmode>${sling.run.modes}</runmode>
                             <contextPath>${http.base.path}</contextPath>
+                            <!-- use Java8 compatible date/number formatting: https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-A20F2989-BFA9-482D-8618-6CBB4BAAE310 -->
+                            <vmOpts>-Xmx1024m -XX:MaxPermSize=256m -Djava.awt.headless=true -Djava.locale.providers=COMPAT,CLDR</vmOpts>
                             <debug>${debug.options}</debug>
                         </server>
                     </servers>