README: Add a note on compiling qboot

Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
Message-Id: <1432561354-26220-1-git-send-email-kchamart@redhat.com>
["make" is enough. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed