[Bug target/62109] __gthr_i486_lock_cmp_xchg missing clobber

[gccbugzilla at limegreensocks dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62109

--- Comment #2 from David <gccbugzilla at limegreensocks dot com> ---
Attaching a patch was just the clearest way I knew to show the problem.

My hope was that posting it here would allow someone who knew how to submit
patches to take this the rest of the way.