Can confirm this seems to be the cause, I’ve made the following overlay and the system now rebuilds with audio:
self: super:
{
alsaLib = super.alsaLib.overrideAttrs (old: rec {
name = "alsa-lib-1.1.8";
src = super.fetchurl {
url = "mirror://alsa/lib/${name}.tar.bz2";
sha256 = "1pxf0zkmps03l3zzd0fr828xhkg6a8hxljmbxzc2cyj2ls9kmp1w";
};
});
}