gitlab-ci: fix pages

This hopefully fixes a failure introduced in
5a0706b238987bf3dcf7dde54556850ee88ccdba:

cp: cannot stat '/builds/wayland/weston/prefix-weston-build-native-meson/share/doc/weston/*': No such file or directory

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

.gitlab-ci.yml

@@ -87,7 +87,7 @@ pages:
   dependencies:
     - build-native-meson-default-options
   script:
-  - export PREFIX=$(pwd)/prefix-weston-build-native-meson
+  - export PREFIX=$(pwd)/prefix-weston-build-native-meson-default-options
   - mkdir public
   - cp -R $PREFIX/share/doc/weston/* public/
   artifacts: