Remove hardcoded gcc version

* configure.ac: Use 'find' to find the brew installed libgccjit libs
instead of a hardcoded path.
10 jobs for feature/native-comp in 169 minutes and 5 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Prep Images
passed #16775
prep-image-base

00:04:37

 
  Build Images
passed #16776
build-image-inotify

00:29:17

 
  Platform Images
passed #16777
build-image-filenotify-gio

00:55:32

passed #16778
build-image-gnustep

01:56:58

 
  Platforms
failed #16779
test-filenotify-gio

00:18:10

passed #16780
test-gnustep

00:02:20

 
  Slow
skipped #16784
test-all-inotify
skipped #16781
test-native-bootstrap-speed0
skipped #16782
test-native-bootstrap-speed1
skipped #16783
test-native-bootstrap-speed2
 
Name Stage Failure
failed
test-filenotify-gio Platforms

make: Leaving directory '/checkout/test'
Running after_script
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
test-filenotify-gio-8ed46b76
Cleaning up file based variables
ERROR: Job failed: exit code 2