meson: Unbreak the non-macOS builds
The name_suffix keyword argument identifies an empty array, not an empty string, as None or null [1]. Using an empty string creates shared objects without any suffix whatsoever on non-macOS environments, which GModule can't load.
Fallout from 8d3367c2
[1] As per the implementation of the BuildTarget class in meson/mesonbuild/build.py