Convert 'thread to mark-stack map empty' assertion into a CHECK

Using LOG(FATAL) doesn't print threads' headers, which is needed to
identify the thread(s) which has a mark-stack assigned.

Bug:144408451
Test: art/test/testrunner/testrunner.py --host
Change-Id: Ib273dd866e00f231ab67d9da7cad14659cbb7c6b
1 file changed