When possible use generated-files-$(FLAG) to disable
some targets (like KEYCODEMAP_FILES).
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NLaurent Vivier <lvivier@redhat.com>
Message-Id: <20190401141222.30034-3-lvivier@redhat.com>