libinput: fix building with debug-gui option

libinput: fix building with debug-gui option

When building libinput with the 'gui' PACKAGECONFIG option, it fails
with:

| Run-time dependency x11 found: YES 1.8.9
| Run-time dependency wayland-client found: YES 1.22.0
| Run-time dependency wayland-protocols found: YES 1.34
| Program wayland-scanner found: NO
|
| ../git/meson.build:578:20: ERROR: Program 'wayland-scanner' not found or not executable
|
| A full log can be found at /home/marc/mnt/yocto-latest/build/tmp/work/core2-64-poky-linux/libinput/1.25.0/build/meson-logs/meson-log.txt
| ERROR: meson failed
| WARNING: exit code 1 from a shell command.

Adding a build dependency on wayland-native fixes the issue.

Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>