exit1 calls the bsdthread_terminate system call on Darwin. Currently
it passes no arguments on 386, arm, and arm64, and an exit status on
amd64. None of these are right. The signature of bsdthread_terminate
is:
int bsdthread_terminate(user_addr_t stackaddr, size_t freesize, uint32_t port, uint32_t sem);
Fix all of the Darwin exit1 implementations to call
bsdthread_terminate with 0 for all of these arguments so it doesn't
try to unmap some random memory, free some random port, or signal a
random semaphore.
This isn't a problem in practice because exit1 is never called.
However, we're about to start using exit1.