Add .mvn/jvm.config and unignore it to fix CI OOM

Change-Id: I66db9f20193721205f021b017d4c5b85f9eee47b
diff --git a/.gitignore b/.gitignore
index 28ab00a..6f8d6c3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 !/.github
 !/.gitlab-ci.yml
 !/.mvn
+!/.mvn/jvm.config
 target
 tmp
 logs