[gnome-icon-theme] install-data-hook fix by Yanko Kaneti <yaneti declera com>

[Jakub Steiner <jimmac src gnome org>]

commit 1577d7c022681dc13860292766ff6fd937b797ac
Author: Arnel A. Borja <kyoushuu yahoo com>
Date:   Mon May 20 09:00:12 2013 +0800

    install-data-hook fix by Yanko Kaneti <yaneti declera com>
    
    https://bugzilla.gnome.org/show_bug.cgi?id=700680

 Makefile.am |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 0c5a3c6..6e7bb1d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -81,7 +81,9 @@ install-data-local:
        fi
 
 install-data-hook:
-       $(GTK_UPDATE_ICON_CACHE) -q $(DESTDIR)$(themedir)
+       if test -z "$(DESTDIR)" ; then \
+               $(GTK_UPDATE_ICON_CACHE) -q $(DESTDIR)$(themedir); \
+       fi
 
 uninstall-hook:
        @rm -f  $(DESTDIR)$(themedir)/icon-theme.cache