Also remove 'requires_installation_of', while also checking sbin
directories in 'have_installed'. The run scripts have been adjusted
accordingly.
Fixes#2853
By now, rump would query its available RAM quota to determine the
memory limit minus some RAM reserved for Genode meta-data. This
does not work when the VFS rump plugin is used as the available
quota belongs to the VFS server. In this case the memlimit should
be set by specifing the RAM in the plugin's config, e.g.:
! <vfs>
! <rump fs="ext2fs" ram="64M" writeabl="yes"/>
! </vfs>
Fixes#2783.
