build: Build demos before tools

That's a sneaky trick so my edit/compile/test cycle goes faster:
I usually use demos for testing so the tools don't have to be linked for
me to start testing.

meson.build

@@ -733,11 +733,11 @@ subdir('gtk/css')
 subdir('gdk')
 subdir('gsk')
 subdir('gtk')
-subdir('tools')
 subdir('modules')
 if get_option('demos')
   subdir('demos')
 endif
+subdir('tools')
 if get_option('build-tests')
   subdir('tests')
   subdir('testsuite')