Since I had trouble figuring this out I thought I would share how I did this.
You need to add 2 parameters to jboss-service.xml in default\deploy\jbossweb-tomcat.sar\META-INF
add this right before
This will create a directory in server/default/tmp that will not get removed on webapp redeploys or on jboss restarts. All compiled jsp pages will be kept so you don't have to wait for a recompile every time you restart jboss. If you make a change to a jsp tomcat will detect it and re-compile it for you.