[retro-gtk] build: Add MAINTAINERCLEANFILES

[Adrien Plazas <aplazas src gnome org>]

commit 91cea934a3d4af92d9ef42dbb6ea9102dbb2e6d6
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Apr 5 14:08:38 2017 +0200

    build: Add MAINTAINERCLEANFILES
    
    This avoids having the content of .flatpak-builder and some other files
    as Git untracked files.

 Makefile.am |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 273c787..02b3f72 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -29,6 +29,11 @@ DISTCLEANFILES = intltool-extract \
        po/.intltool-merge-cache \
        $(NULL)
 
+MAINTAINERCLEANFILES = \
+       $(GITIGNORE_MAINTAINERCLEANFILES_TOPLEVEL) \
+       $(GITIGNORE_MAINTAINERCLEANFILES_MAKEFILE_IN) \
+       .flatpak-builder \
+       $(NULL)
 
 # Remove doc directory on uninstall
 uninstall-local: