meson: set minimum required version

meson.build

@@ -1,6 +1,6 @@
 project('iridium', 'c',
   version: '0.1.0',
-  meson_version: '>= 0.40.0',
+  meson_version: '>= 0.45.0',
 )
 
 cc = meson.get_compiler('c')