Nixpkgs on unstable has removed stdenv.lib
as they've been warning for a while now. This removes the extra references to it in the flake.nix
I'm not entirely sure if this is right, but I figured it was trivial enough to give a quick try using the GH Editor while I was waiting for a job to finish
Q3DGWF3WFZUXUPFCSG7M52OXK5I4QUNAWFQTDEUY5UEWC2XWRWUQC