do locatedb as part of the build process

"works for me" deraadt@

src/etc/mtree/4.4BSD.dist

@@ -1,4 +1,4 @@
-#	$OpenBSD: 4.4BSD.dist,v 1.247 2014/04/22 10:24:29 reyk Exp $
+#	$OpenBSD: 4.4BSD.dist,v 1.248 2014/07/09 19:23:28 espie Exp $
 
 /set type=dir uname=root gname=wheel mode=0755
 # .
@@ -353,6 +353,11 @@ debug		gname=bin uname=root mode=0755
 # ./usr/lib/debug
 ..
 
+# ./usr/lib/locate
+locate	gname=bin uname=root mode=0755
+# ./usr/lib/locate
+..
+
 # ./usr/lib/pkgconfig
 pkgconfig	gname=bin uname=root mode=0755
 # ./usr/lib/pkgconfig