desktop/gnome-photos: Check executable update-gdk-pixbuf-loaders.

Signed-off-by: Dave Woodfall <dave@slackbuilds.org>

Signed-off-by: Willy Sudiarto Raharjo <willysr@slackbuilds.org>

desktop/gnome-photos/gnome-photos.SlackBuild

@@ -79,7 +79,9 @@ find -L . \
 # gnome-photos fails to build in a fresh build environment, complaining
 # that it doesn't recognize svg formats. Updating the pixbuf loaders
 # gets it working:
-/usr/bin/update-gdk-pixbuf-loaders
+if [ -x /usr/bin/update-gdk-pixbuf-loaders ]; then
+  /usr/bin/update-gdk-pixbuf-loaders
+fi
 
 mkdir build
 cd build