upstream: Check if we can copy sshd or need to use sudo to do so

during reexec test. Skip test if neither can work.  Patch from anton@, tweaks
from me.

OpenBSD-Regress-ID: 731b96ae74d02d5744e1f1a8e51d09877ffd9b6d

regress/reexec.sh

@@ -1,4 +1,4 @@
-#	$OpenBSD: reexec.sh,v 1.12 2017/08/07 03:52:55 dtucker Exp $
+#	$OpenBSD: reexec.sh,v 1.13 2023/01/19 07:53:45 dtucker Exp $
 #	Placed in the Public Domain.
 
 tid="reexec tests"
@@ -49,7 +49,7 @@ if [ "$os" != "cygwin" ]; then
 verbose "test reexec fallback"
 
 start_sshd_copy
-rm -f $SSHD_COPY
+$SUDO rm -f $SSHD_COPY
 
 copy_tests