bulid(nix): use new fenix for dev shell

flake.lock

@@ -115,6 +115,25 @@
         "type": "github"
       }
     },
+    "new-fenix": {
+      "inputs": {
+        "nixpkgs": "nixpkgs_4",
+        "rust-analyzer-src": "rust-analyzer-src_2"
+      },
+      "locked": {
+        "lastModified": 1734417396,
+        "narHash": "sha256-32x1Z+Pz3Jv0cK9EG56cFTKXy/mZ/c+Ikxw+aVfKHp4=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "a18d41b26e998e95a598858fdb86ba22fb5da47d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
     "nix-filter": {
       "locked": {
         "lastModified": 1730207686,
@@ -175,6 +194,22 @@
       }
     },
     "nixpkgs_4": {
+      "locked": {
+        "lastModified": 1734119587,
+        "narHash": "sha256-AKU6qqskl0yf2+JdRdD0cfxX4b9x3KKV5RqA6wijmPM=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "3566ab7246670a43abd2ffa913cc62dad9cdf7d5",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_5": {
       "locked": {
         "lastModified": 1731139594,
         "narHash": "sha256-IigrKK3vYRpUu+HEjPL/phrfh7Ox881er1UEsZvw9Q4=",
@@ -196,8 +231,9 @@
         "fenix": "fenix",
         "flake-utils": "flake-utils_2",
         "naersk": "naersk",
+        "new-fenix": "new-fenix",
         "nix-filter": "nix-filter",
-        "nixpkgs": "nixpkgs_4"
+        "nixpkgs": "nixpkgs_5"
       }
     },
     "rust-analyzer-src": {
@@ -217,6 +253,23 @@
         "type": "github"
       }
     },
+    "rust-analyzer-src_2": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1734386068,
+        "narHash": "sha256-Py025JiD9lcPmldB7X1AEjq3WBTS60jZUJRtTDonmaE=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "0a706f7d2ac093985eae317781200689cfd48b78",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    },
     "systems": {
       "locked": {
         "lastModified": 1681028828,

flake.nix

@@ -1,14 +1,19 @@
 {
   description = "Delta Chat core";
   inputs = {
+    # Old Rust to build releases.
     fenix.url = "github:nix-community/fenix?rev=85f4139f3c092cf4afd9f9906d7ed218ef262c97";
+
+    # New Rust for development shell.
+    new-fenix.url = "github:nix-community/fenix";
+
     flake-utils.url = "github:numtide/flake-utils";
     naersk.url = "github:nix-community/naersk";
     nix-filter.url = "github:numtide/nix-filter";
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
     android.url = "github:tadfisher/android-nixpkgs";
   };
-  outputs = { self, nixpkgs, flake-utils, nix-filter, naersk, fenix, android }:
+  outputs = { self, nixpkgs, flake-utils, nix-filter, naersk, fenix, new-fenix, android }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
@@ -539,13 +544,13 @@
           let
             pkgs = import nixpkgs {
               system = system;
-              overlays = [ fenix.overlays.default ];
+              overlays = [ new-fenix.overlays.default ];
             };
           in
           pkgs.mkShell {
 
             buildInputs = with pkgs; [
-              (fenix.packages.${system}.complete.withComponents [
+              (new-fenix.packages.${system}.complete.withComponents [
                 "cargo"
                 "clippy"
                 "rust-src"