s390-ccw remains a bit more complex, because the -march=z900 test is done
only for the native cross compiler.  Otherwise, all that is needed is
to pass the (now mandatory) target argument to write_target_makefile.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220929114231.583801-29-alex.bennee@linaro.org>