--version is a GNUism which BSD diff doesn't support

--- configure.orig	2018-01-24 22:25:44 UTC
+++ configure
@@ -170,7 +170,7 @@ for t in ${all_targets}; do
     [ -f "${source_path}/${t}.mk" ] && enable_feature ${t}
 done
 
-if ! diff --version >/dev/null; then
+if ! hash diff 2>/dev/null; then
   die "diff missing: Try installing diffutils via your package manager."
 fi
 
