meson: fix incorrect use of global arguments to set symbol visibility

meson: fix incorrect use of global arguments to set symbol visibility

add_global_arguments applies to all subprojects, or more usually, fails.
The meson docs suggest that add_project_arguments is probably preferable
for this reason.

However, in this case it should only be applied to a single library as a
workaround for supporting older versions of meson. Move it to a
per-target c_args instead, for the same effect.