bitbake.conf: Use wayland distro feature for native builds

The wayland-scanner is missing from SDKs with weston, but the weston build
requires wayland-scanner. Allow the distro feature in order to include
the wayland-scanner packages via nativesdk-packagegroup-sdk-host.bb.

Signed-off-by: Tom Hochstein <tom.hochstein@nxp.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>