Also extract makepkg.conf.d from devtools

We only [copy the $arch-makepkg.conf](https://github.com/archlinux/archlinux-repro/blob/6729ed370c2ac197afbc49d7921631d6e575431f/repro.in#L517) but we should also copy makepkg.conf.d like [makerepropkg does](https://gitlab.archlinux.org/archlinux/devtools/-/commit/fb4bf96d245b145e766c22547e67ff94f0297961). This should make rust packages reproducible