meson: refactor link_language usage

Refactor the way link_language is specified to ensure a correct value (the default one or the one provided by the module) is always used. Before, [] was allowed as a default value to fallback to meson autodetection but it has been removed when link_language and other kwargs have been typed¹ in the interpreter, leading to the followin error in meson 1.3.1

../modules/meson.build:295:17: ERROR: library keyword argument 'link_language' was of type array[] but should have been one of: str, NoneType

1. https://github.com/mesonbuild/meson/commit/0f23dc5b03fda2e8958903eb25587a7e4e2daa67 ↩