At the moment the SPARC FS machine configuration comes with a hardcoded value for using the Solaris 10 disk image from the OpenSPARC tarball. The --disk-image option is completely ignored for SPARC. This simple patch modifies the behavior so that --disk-image option is both taken into account and also required. This makes it possible to easily change SPARC FS images without having to modify the configuration files.

successfully ran SPARC FS simulation with --disk-image pointed to a HelenOS ISO image
successfully ran SPARC FS simulation with --disk-image pointed to the Solaris 10 image from the OpenSPARC tarball
verified that not specifying a --disk-image option results in a sensible error message