meson: Various fixes

meson: Various fixes

- Add missing lcms dependencies. That's needed when lcms is a subproject
  otherwise those targets does not find its headers.
- Add lcms2 wrap so meson can build it as subproject in case the
  dependency is not found on system.
- Fix couple meson warnings
- Use meson.override_dependency() so babl can be used as subproject
  without hardcoding "babl_dep" variable name in main project.