[gnome-shell] build: Fix distcheck

[Florian MÃllner <fmuellner src gnome org>]

commit fd3be5b7de7be2867536d83382c115cc997d40f9
Author: Florian MÃllner <fmuellner gnome org>
Date:   Mon Aug 6 16:11:17 2012 +0200

    build: Fix distcheck
    
    I knew it had to be something simple ...

 src/Makefile-calendar-server.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/Makefile-calendar-server.am b/src/Makefile-calendar-server.am
index bad727e..635c4ea 100644
--- a/src/Makefile-calendar-server.am
+++ b/src/Makefile-calendar-server.am
@@ -33,5 +33,5 @@ EXTRA_DIST += 							  \
 	calendar-server/org.gnome.Shell.CalendarServer.service.in \
 	$(NULL)
 
-CLEANFILES = \
+CLEANFILES += \
 	$(desktop_DATA)