[gnome-calendar] Specify Meson as build system.

[Arnaud B. <arnaudb src gnome org>]

commit 8ff016e5694b61054a724a34415476b7cac35bcf
Author: Arnaud B <arnaud bonatti gmail com>
Date:   Sat Feb 24 14:37:42 2018 +0000

    Specify Meson as build system.

 org.gnome.Calendar.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/org.gnome.Calendar.json b/org.gnome.Calendar.json
index fad21488..81c337b4 100644
--- a/org.gnome.Calendar.json
+++ b/org.gnome.Calendar.json
@@ -154,6 +154,7 @@
         },
         {
             "name" : "gnome-calendar",
+            "buildsystem" : "meson",
             "sources" : [
                 {
                     "type" : "git",