Note that we need to clean objdir for the OpenSSL update.

UPDATING

@@ -1,4 +1,4 @@
-$NetBSD: UPDATING,v 1.297 2018/07/17 19:13:53 joerg Exp $
+$NetBSD: UPDATING,v 1.298 2018/09/24 13:18:35 martin Exp $
 
 This file (UPDATING) is intended to be a brief reference to recent
 changes that might cause problems in the build process, and a guide for
@@ -19,6 +19,11 @@ See also: BUILDING, build.sh, Makefile.
 Recent changes:
 ^^^^^^^^^^^^^^^
 
+20180924:
+	A newer OpenSSL version has been imported. If you are doing
+	update builds, make sure to remove all old obj dirs, like:
+	cd /usr/obj && find . -type d -name openssl | xargs rm -rf
+
 20180717:
 	On aarch64 int64_t and related types have changed from long long
 	to long. This requires recompiling all C++ binaries.