I guess the problem I am thinking of is that there is only one file but two compilers. This implies that there ought to be compiler specific versions installed. Perhaps though this is just a Debian/Fedora/… problem. They assume one and only one pc file per library.

There is also the issue that Meson compiled D libraries are not dong the same as GtkD, hence the question. The canonical Meson pc file does not have the -L prefix on library flags.