Slow Compilation of Small Projects

[R0b0t1 <r030t1 gmail com>]

Hello,

The example at https://developer.gnome.org/gtkmm-tutorial/stable/sec-basics-simple-example.html.en
compiles very slowly. I attempted to make some improvements, mainly
not including gtkmm.h but instead including only gtkmm/window.h.
However, compilation is still very slow, taking a number of seconds.
Is it the linking step? Is there anything I can do to speed
compilation?

Build:

g++ -std=gnu++1z -Wall -pedantic `pkg-config gtkmm-3.0 --cflags --libs` \
    -o gtktest gtktest.cc


Program:

#include <gtkmm/window.h>

int
main(int argc, char *argv[])
{
    auto app = Gtk::Application::create(
            argc, argv, "org.gtkmm.examples.base"
    );

    Gtk::Window window;
    window.set_default_size(200, 200);

    return app->run(window);
}