meson: always include contrib/libvhost-user

libvhost-user is needed when CONFIG_LINUX is set. The CONFIG_VHOST_USER
check in meson.build is incorrect.

In fact, no explicit check is needed since this dependency is not built
by default. If something declares a dependency on libvhost-user then it
will be built, otherwise it won't be built (i.e. on non-Linux hosts).

This fixes ./configure --disable-vhost-user && make.

Fixes: bc15e44 ("configure: introduce --enable-vhost-user-blk-server")
Reported-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201106210340.698771-1-stefanha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

meson.build

@@ -1450,11 +1450,7 @@ trace_events_subdirs += [
   'util',
 ]
 
-vhost_user = not_found
-if 'CONFIG_VHOST_USER' in config_host
-  subdir('contrib/libvhost-user')
-endif
-
+subdir('contrib/libvhost-user')
 subdir('qapi')
 subdir('qobject')
 subdir('stubs')