[gtk/gtk-3-24: 1/2] build: Avoid redefining EXTRA_DIST

[Matthias Clasen <matthiasc src gnome org>]

commit 62412cbcf4c75c190ce0cfff1192a46e0d9b5717
Author: Philip Chimento <philip endlessm com>
Date:   Thu Sep 19 15:35:13 2019 -0700

    build: Avoid redefining EXTRA_DIST
    
    EXTRA_DIST is defined here and in Makefile.decl. The build system will
    complain about that.

 demos/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/demos/Makefile.am b/demos/Makefile.am
index f780869ead..024fcb3a75 100644
--- a/demos/Makefile.am
+++ b/demos/Makefile.am
@@ -3,7 +3,7 @@ include $(top_srcdir)/Makefile.decl
 
 SUBDIRS = gtk-demo widget-factory icon-browser
 
-EXTRA_DIST = \
+EXTRA_DIST += \
        meson.build
 
 -include $(top_srcdir)/git.mk