error: The name `STOCK_FILE' does not exist in the context of `Gtk'
return widget.render_icon (Gtk.STOCK_FILE, Gtk.IconSize.MENU, null);
^^^^^^^^^^^^^^
error: The name `STOCK_CLOSE' does not exist in the context of `Gtk'
var action_close = new Midori.ContextAction ("TabClose", null, null, Gtk.STOCK_CLOSE);
^^^^^^^^^^^^^^^
I can confirm the build failure on macOS High Sierra.
Looks like our port is out of date. Our port is for version 0.5.11 but the current upstream version is either 6.0 (according to the web page) or 7.0 (according to GitHub). Someone will need to update the port.