While it is useful to run these images using TCG their performance
will not be anything like the native guests. Don't do it by default.

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/393


Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211115142915.3797652-4-alex.bennee@linaro.org>