On each execution the output buffer is overriden when run_genode_until
is executed multiple times. Run scripts, that depend on extracting
information after several execution steps, e.g. noux_net_netcat, will
fail to do so. Therefore, we append the newly captured log output to
the old output buffer.
Issue #1327.
and move it close to run_genode_until implementation.
Somehow the "match_max -d" gets ignored if it is to far away and some
our run scripts fails because the buffer contains not all information
(seen for affinity.run on a 8 core machine)