The executable of the LibreOffice app (which as such at the moment
doesn't work, since the tiled rendering changes) is built using
gbuild, and thus we can't generate the native-code snippet in the
CustomTarget that builds the app bundle, but need it already when
building the executable. This is one wayt to handle that.

Change-Id: Ifdab40c970e93b1f2608cefc637df8a8e5396efe