macOS: Fixup plugin signing.

Use `find` to find plugins.

Change-Id: I6df8877547ecbd19644a846e5cb02e8b65f19e61
Reviewed-on: https://code.wireshark.org/review/23730
Reviewed-by: Gerald Combs <gerald@wireshark.org>

packaging/macosx/osx-app.sh

@@ -624,7 +624,7 @@ if [ -n "$CODE_SIGN_IDENTITY" ] ; then
 	done
 
 	echo "Signing plugins"
-	for plugin in $pkgplugin/*.so ; do
+	find $pkgplugin -type f -name "*.so" | while read plugin ; do
 		codesign_file "$plugin"
 	done