only a few places left to convert to pkgconf_buffer_t in pkgconf now :)

and then we will be able to stop using strlcpy/strlcat (which was a bad engineering decision, but i was also much younger then)

@ariadne genuinely interested: what's wrong with strlcpy and strlcat?
@rnd silent truncation, but that isn't a practical concern in pkgconf I guess.