[gnome-builder] flatpak: use meson to build devhelp

[Christian Hergert <chergert src gnome org>]

commit 31669abccf0df8ef2c8395f08d94c76732061648
Author: Christian Hergert <chergert redhat com>
Date:   Fri Mar 23 14:33:29 2018 -0700

    flatpak: use meson to build devhelp

 build-aux/flatpak/org.gnome.Builder.json | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index 7a1db2078..6dabe7cbd 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -520,8 +520,11 @@
         },
         {
             "name" : "devhelp",
+            "buildsystem" : "meson",
+            "builddir" : true,
             "config-opts" : [
-                "--disable-compile-warnings"
+                "--libdir=/app/lib",
+                "--buildtype=debugoptimized"
             ],
             "cleanup" : [
                 "/bin/*",