fix: remove fenix flake input

By now it is possible to use cargo-llvm-cov with the nixpkgs built-in
llvm tools, thus no need for a nightly rust with the llvm-tools-preview.
Therefore, fenix as a dependency is removed.

Signed-off-by: wucke13 <wucke13+github@gmail.com>

flake.lock

@@ -1,26 +1,5 @@
 {
   "nodes": {
-    "fenix": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ],
-        "rust-analyzer-src": "rust-analyzer-src"
-      },
-      "locked": {
-        "lastModified": 1728282832,
-        "narHash": "sha256-I7AbcwGggf+CHqpyd/9PiAjpIBGTGx5woYHqtwxaV7I=",
-        "owner": "nix-community",
-        "repo": "fenix",
-        "rev": "1ec71be1f4b8f3105c5d38da339cb061fefc43f4",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "fenix",
-        "type": "github"
-      }
-    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -77,30 +56,12 @@
     },
     "root": {
       "inputs": {
-        "fenix": "fenix",
         "flake-utils": "flake-utils",
         "nix-vm-test": "nix-vm-test",
         "nixpkgs": "nixpkgs",
         "treefmt-nix": "treefmt-nix"
       }
     },
-    "rust-analyzer-src": {
-      "flake": false,
-      "locked": {
-        "lastModified": 1728249780,
-        "narHash": "sha256-J269DvCI5dzBmPrXhAAtj566qt0b22TJtF3TIK+tMsI=",
-        "owner": "rust-lang",
-        "repo": "rust-analyzer",
-        "rev": "2b750da1a1a2c1d2c70896108d7096089842d877",
-        "type": "github"
-      },
-      "original": {
-        "owner": "rust-lang",
-        "ref": "nightly",
-        "repo": "rust-analyzer",
-        "type": "github"
-      }
-    },
     "systems": {
       "locked": {
         "lastModified": 1681028828,

flake.nix

@@ -3,10 +3,6 @@
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
     flake-utils.url = "github:numtide/flake-utils";
 
-    # for rust nightly with llvm-tools-preview
-    fenix.url = "github:nix-community/fenix";
-    fenix.inputs.nixpkgs.follows = "nixpkgs";
-
     nix-vm-test.url = "github:numtide/nix-vm-test";
     nix-vm-test.inputs.nixpkgs.follows = "nixpkgs";
     nix-vm-test.inputs.flake-utils.follows = "flake-utils";
@@ -150,18 +146,21 @@
                 nodePackages.prettier
                 nushell # for the .ci/gen-workflow-files.nu script
                 proverif-patched
-                inputs.fenix.packages.${system}.complete.toolchain
                 pkgs.cargo-llvm-cov
                 pkgs.grcov
+                pkgs.rust-bin.stable.latest.complete
               ];
             };
             devShells.coverage = pkgs.mkShell {
               inputsFrom = [ pkgs.rosenpass ];
               nativeBuildInputs = [
-                inputs.fenix.packages.${system}.complete.toolchain
                 pkgs.cargo-llvm-cov
                 pkgs.grcov
+                pkgs.rustc.llvmPackages.llvm
               ];
+              env = {
+                inherit (pkgs.cargo-llvm-cov) LLVM_COV LLVM_PROFDATA;
+              };
             };
 
             checks =