meson: add sizeof checks for meson

this fixes the building for systems where int and long does not have the
same size.

Differential Revision: https://phab.enlightenment.org/D7143

header_checks/meson.build

@@ -174,4 +174,7 @@ endif
 
 if config_h.has('HAVE_KEVENT')
   config_h.set('HAVE_NOTIFY_KEVENT', '1')
-endif
+endif
+
+config_h.set('SIZEOF_INT', cc.sizeof('int'))
+config_h.set('SIZEOF_LONG', cc.sizeof('long'))