doc: Add a flake.nix to ease build environment setup

Author: ithinuel

README.md

@@ -55,6 +55,8 @@ If you aren't using a debugger (or want to use other debugging configurations),
 <details open="open">
   <summary><h2 style="display: inline-block" id="installation-of-development-dependencies">Installation of development dependencies</h2></summary>
 
+If you are using Nix, you can use the `devShell` made available in `flake.nix`. Otherwise, you can follow these commands (provided you already have [`Rustup`](https://rustup.rs/) installed):
+
 ```sh
 rustup target install thumbv6m-none-eabi
 cargo install flip-link

flake.lock

@@ -0,0 +1,29 @@
+{
+  description = "Flake configuration for my systems";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+    utils.url = "github:numtide/flake-utils";
+    rust-overlay.url = "github:oxalica/rust-overlay";
+    rust-overlay.inputs.nixpkgs.follows = "nixpkgs";
+  };
+
+  outputs = { nixpkgs, utils, rust-overlay, ... }:
+    utils.lib.eachDefaultSystem (system:
+      let pkgs = import nixpkgs { inherit system; overlays = [ (import rust-overlay) ]; };
+      in {
+        devShells.default = pkgs.mkShell {
+          buildInputs = [
+            pkgs.flip-link
+            (pkgs.rust-bin.stable.latest.default.override {
+              extensions = [
+                "rust-src"
+                "clippy"
+                "rust-analyzer"
+              ];
+              targets = [ "thumbv6m-none-eabi" ];
+            })
+          ];
+        };
+      });
+}