meson: Bump required version to 0.40

link_whole needs that, and we need that. Reported by Chris Wilson.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Acked-by: Petri Latvala <petri.latvala@intel.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Acked-by: Radoslaw Szwichtenberg <radoslaw.szwichtenberg@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/meson.build b/meson.build
index 2b49a0d..0858354 100644
--- a/meson.build
+++ b/meson.build
@@ -4,7 +4,8 @@
           'warning_level=2',
           'c_std=gnu99',
         ],
-	license : 'MIT')
+	license : 'MIT',
+	meson_version : '>0.40.0')
 
 cc = meson.get_compiler('c')