BUILD: wdt: only test for SI_TKILL when compiled with thread support

SI_TKILL is not necessarily defined on older systems and is used only
with the pthread_kill() call a few lines below, so it should also be
subject to the USE_THREAD condition.

(cherry picked from commit 0627815f701ee6549bcf4c2611df8ccdd3bd3fc9)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit c32c7e3b39711c329b759a5767276b543913621a)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed