indicator-messages does not update icon cache after installing icons

[Charles Kerr]

The icons are installed into $(datadir)/icons/hicolor, but gtk-update-icon-cache is run on $(pkgdatadir)/icons/hicolor

So for example if you configure this way:

  > $ ./configure --enable-localinstall --prefix=/tmp/test

You get this error:

  > Updating Gtk icon cache.
  > gtk-update-icon-cache: Failed to open file /tmp/test/share/indicator-messages/icons/hicolor/.icon-theme.cache :
  > No such file or directory
  > make[3]: [update-icon-cache] Error 1 (ignored)