This fixes the default use-case for developers when they put their
install prefix somewhere where the system `LD_LIBRARY_PATH` does not
point. Before this, `kresd` would fail to start after `ninja install`
because it would not be able to find the `libkres.so` library.

The original workaround to this was to use `meson configure
-Ddefault_library=static`, but firstly, we would like it to be working
with the default settings, and secondly, we would like to have it as
similar to what most users will encounter as possible.