dnsmasq: fix cross-compilation
dnsmasq: fix cross-compilation

This is done by specifying pkg-config in the makeFlags, ensuring that
the correct pkg-config is injected.

Depends on changes that are currently only in staging:

- 07ecf87693fec1032c19ba1f5b41dc9cf260abb2
- 4f6ec19dbc322d7ce8df9108b76e0db79682353e

See https://github.com/NixOS/nixpkgs/pull/114902 for those changes.

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