Added gnome-theme-standard to the main build

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
Bumped cairo version to 1.12.14

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
Add libspectre and gtkparasite

Just for testing. Those are not built by default.

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>
Fix grammar

Signed-off-by: Germán Poo-Caamaño <gpoo@gnome.org>