Some tests requires specific GC flags. When extra GC options are added by the test framework, then the test wiill fail.

Function removeGcOpts() in testlibrary/jdk/testlibrary/Utils.java is used to remove extra GC options from the command line. That function currently removes all options with pattern "-XX:+-Use*GC". It should also remove the following options:
-Xconcgc
-Xincgc