Test to exercise signal delivery during a blocked pipe send.

[rwatson]

Test to trigger #1045 without the more complex IPC context that the original test required for other purposes.

[bsdjhb]

Suggested change

	{
	}
	{
	}

[bsdjhb]

Is it really a successful test if you write the entire buffer without getting interrupted? If you want to ensure that the write was interrupted, then I think what you want to do instead might be something like:

static volatile sig_atomic_t alarm_fired;

static void
sigalrm_handler(...)
{
    alarm_fired = 1;
}

CHERIBSDTEST(...)
{
   ...
   len = write(fds[0], buffer, sizeof(buffer));
   if (len == -1 && errno != EINTR)
       cheribsdtest_failure_err("write");
   /* we probably have some sort of wrapper for this */
   if (alarm_fired == 0)
       cheribsdtest_failure("failed to interrupt write");

Even this is somewhat racy as in theory the handler could fire before or after the write(), but those races are probably rare enough to ignore.