The current test case leaves detached processes running at the end of
the test. This patch changes the test to use a barrier wait to ensure all
processes exit cleanly at the end of the tests.
gdb/testsuite/ChangeLog:
2021-06-02 Carl Love <cel@us.ibm.com>
* gdb.threads/threadapply.c: Add global mybarrier.
(main): Add pthread_barrier_init.
(thread_function): Replace while loop with myp increment and
pthread_barrier_wait.