[geary] Update flatpak-builder manifest to use meson build.

[Michael Gratton <mjog src gnome org>]

commit 3606bade04da2fbae543dc56b20e1258e624b4e6
Author: Michael James Gratton <mike vee net>
Date:   Fri Jan 12 16:21:19 2018 +1100

    Update flatpak-builder manifest to use meson build.

 org.gnome.Geary.json |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/org.gnome.Geary.json b/org.gnome.Geary.json
index d1de0a4..99b73c0 100644
--- a/org.gnome.Geary.json
+++ b/org.gnome.Geary.json
@@ -110,6 +110,8 @@
         },
         {
             "name": "geary",
+            "buildsystem": "meson",
+            "builddir": true,
             "sources": [
                 {
                     "type": "git",