Fix a footgun. In my case, I had a couple of build ("output")
directories sitting around.
rm -rf build-*
Was confused for a bit why a meson.build file was missing.
Probably also helps with autocompletion.
I tried meson-build-support first, but I had to add something like
a nix- prefix, in order to make meson happy. They've reserved the
meson- prefix.
... and remove a few unused arguments.
This adds pkg-config to a two or three packages that don't use it,
but we shouldn't let that bother us. It's like our personal stdenv.
