Anything but --type sync (which is the default) suppresses output
entirely, which makes no sense.
Dates back to the initial commit c17d990. Commit message says
"Currently only generators for synchronous qapi/qmp functions are
supported", so maybe output other than "synchronous qapi/qmp" was
planned at the time, to be selected with --type.
Should other kinds of output ever materialize, we can put the option
back.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
72aaa73a4a