Fix a portability issue

The issue is using the GNU `find` extension `-wholename`. Brian Callahan
of OpenBSD found the problem and proposed the fix, which is in this
commit.

configure.sh

@@ -295,7 +295,7 @@ gen_file_list() {
 		while [ "$#" -ge 1 ]; do
 			a="$1"
 			shift
-			args="$args ! -wholename src/${a}"
+			args="$args ! -path src/${a}"
 		done
 
 	else