When deleting empty directories prior to building the release tarballs,

pass the "-empty" flag to find(1).  This change has no effect other
than to get rid of a few pages of "rmdir: ...: Directory not empty"
error messages.  (Note that the "-empty" flag has been supported by
find(1) since 4.3-RELEASE.)

release/Makefile

@@ -650,7 +650,7 @@ release.5:
 	# Remove all the directories we don't need.
 	-cd ${RD}/trees && \
 		(find ${OTHER_DISTS} -path '*/var/empty' | xargs chflags noschg; \
-		find ${OTHER_DISTS} -depth -type d -print | xargs rmdir)
+		find ${OTHER_DISTS} -depth -type d -empty -print | xargs rmdir)
 	touch ${.TARGET}
 
 #