Add a regression test for r318191

[markj]

Summary

The test simply attempts to attach to a multi-threaded process in which
threads are blocked on a file lock and thus sleeping in an SBDRY
section.

[badger]

tests/sys/kern/ptrace_test.c

3059 ↗

(On Diff #28249)

I think "./ptrace.XXXXXX" would be a better file path. I believe the test framework will clean up the working directory, whereas something in /tmp would be left if the test bails out before unlink()ing.

[markj]

• Create the tmpfile in the current directory.

[markj]

tests/sys/kern/ptrace_test.c

3059 ↗

(On Diff #28249)

Thanks, fixed.