xbps-src: make -K work when run_func returns an error.

xbps-src/shutils/chroot.sh.in

@@ -314,7 +314,7 @@ xbps_chroot_handler()
 		env IN_CHROOT=1 LANG=C \
 			${chroot_cmd} $XBPS_MASTERDIR /bin/sh || rv=$?
 	else
-		[ -n "$KEEP_WRKSRC" ] && arg="-C"
+		[ -n "$KEEP_WRKSRC" ] && arg="$arg -C"
 		[ -n "$KEEP_AUTODEPS" ] && arg="$arg -K"
 		[ -n "$DESTDIR_ONLY_INSTALL" ] && arg="$arg -D"