[gnome-builder] flatpak: use /var/run/host/etc for flatpak sysconfdir

[Christian Hergert <chergert src gnome org>]

commit 58211c12d822ecdba611a36d9e3bd6d4ef4484a5
Author: Christian Hergert <chergert redhat com>
Date:   Tue Jan 14 13:16:17 2020 -0800

    flatpak: use /var/run/host/etc for flatpak sysconfdir
    
    To ensure system flatpak installations can be seen.
    
    Fixes #1125

 build-aux/flatpak/org.gnome.Builder.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/build-aux/flatpak/org.gnome.Builder.json b/build-aux/flatpak/org.gnome.Builder.json
index b477eb88d..94bac6212 100644
--- a/build-aux/flatpak/org.gnome.Builder.json
+++ b/build-aux/flatpak/org.gnome.Builder.json
@@ -467,7 +467,8 @@
                 "--disable-seccomp",
                 "--disable-sandboxed-triggers",
                 "--disable-system-helper",
-                "--with-system-install-dir=/var/lib/flatpak"
+                "--with-system-install-dir=/var/lib/flatpak",
+                "--sysconfdir=/var/run/host/etc"
             ],
             "cleanup" : [
                 "/bin/flatpak-bisect",