Also don't miss lib.addMetaAttrs:
> lib.addMetaAttrs { platforms = drv.meta.platforms ++ [ "x86_64-darwin" ] } drv
is a bit neater than having to go all:
> drv.overrideAttrs (oldAttrs: { meta = oldAttrs.meta // { platforms = oldAttrs.meta.platforms ++ [ "x86_64-darwin" ]; }; })
#nix