[gnome-builder] build: bump minimum meson version

[Christian Hergert <chergert src gnome org>]

commit 05e4b60ecd58c2f404d1c81bda3e6e96fa2ac37b
Author: Christian Hergert <chergert redhat com>
Date:   Fri Jul 13 09:24:33 2018 -0700

    build: bump minimum meson version
    
    This fixes a warning in custom_target

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 745aa857c..6c41cb083 100644
--- a/meson.build
+++ b/meson.build
@@ -1,7 +1,7 @@
 project('gnome-builder', 'c',
           license: 'GPL3+',
           version: '3.29.3',
-    meson_version: '>= 0.44.0',
+    meson_version: '>= 0.47.0',
   default_options: [ 'c_std=gnu11',
                      'cpp_std=c++11',
                      'warning_level=2',