I had the same problem a while ago and this is my solution:
1- in the pre_group_script (or pre_session_script depending on your vsif), you add -elaborate and +nclibdirname+INCA_lib to irun, to compile but not simulate the stuff.
2- in the run_script of all tests, add -R and +nclibdirname+../INCA_lib to irun, which uses the previously compiled files. Since I added the -elaborate to group, I could point the directory to one level up. In case you add the elaborating script to the session, you need to point the run scripts to two directory levels up (../../).