[gnome-builder] flatpak: restore buildtype configure option

[Jordan Petridis <jpetridis src gnome org>]

commit 0b35d581f6536e5be41c301a11267983e27f4857
Author: Jordan Petridis <jordan centricular com>
Date:   Tue Aug 4 01:36:26 2020 +0300

    flatpak: restore buildtype configure option
    
    It was deleted accidently in the last commit. Oops!

 build-aux/flatpak/org.gnome.Builder.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index 73f6a642d..95bf6fe36 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -636,6 +636,7 @@
             "builddir" : true,
             "config-opts" : [
                 "--libdir=lib",
+                "--buildtype=debugoptimized",
                 "-Dctags_path=/app/bin/ctags",
                 "-Dtcmalloc=true",
                 "-Dpython_libprefix=python3.7",