add test config

Author: kolea2

.kokoro/build.sh

@@ -47,6 +47,7 @@ set +e
 
 case ${JOB_TYPE} in
 test)
+    export MAVEN_OPTS="-Xmx1024m -XX:MaxPermSize=128m"
     mvn test -B -Dclirr.skip=true -Denforcer.skip=true
     RETURN_CODE=$?
     ;;