Do not automatically set font-size on macOS

freetype on macOS does not scale fonts, font-scale and ui_scale
have to remain at 100% otherwise other UI elements change size
while the font does not.

gtk2_ardour/ardour_ui.cc

@@ -216,9 +216,11 @@ static const gchar *_record_mode_strings[] = {
 static bool
 ask_about_configuration_copy (string const & old_dir, string const & new_dir, int version)
 {
+#ifndef __APPLE__
 	/* guess screen scaling */
 	UIConfiguration::instance ().set_font_scale (1024 * guess_default_ui_scale ());
 	UIConfiguration::instance ().reset_dpi ();
+#endif
 
 	ArdourMessageDialog msg (string_compose (
 	                          _("%1 %2.x has discovered configuration files from %1 %3.x.\n\n"

gtk2_ardour/utils.cc

@@ -645,6 +645,9 @@ ARDOUR_UI_UTILS::key_is_legal_for_numeric_entry (guint keyval)
 int
 ARDOUR_UI_UTILS::guess_default_ui_scale ()
 {
+#ifdef __APPLE__
+	return 100;
+#else
 	gint width = 0;
 	gint height = 0;
 	GdkScreen* screen = gdk_display_get_screen (gdk_display_get_default (), 0);
@@ -674,6 +677,7 @@ ARDOUR_UI_UTILS::guess_default_ui_scale ()
 	} else {
 		return 250;
 	}
+#endif
 }
 
 void