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.
Edited by Xavier Claessens