Add flake

flake.nix

@@ -0,0 +1,61 @@
+{
+  description = "Ada development environment with Alire";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            # Ada
+            gnat
+            gprbuild
+            alire
+
+            # Toolchain
+            gcc
+            binutils
+
+            # Build Tools
+            gnumake
+            cmake
+            pkg-config
+
+            # Debugging
+            gdb
+
+            # Utilities
+            git
+            which
+            file
+          ];
+
+          shellHook = ''
+            export ADA_PROJECT_PATH="$PWD''${ADA_PROJECT_PATH:+:$ADA_PROJECT_PATH}"
+
+            echo "Ada + Alire development shell"
+            echo "--------------------------------"
+
+            command -v alr >/dev/null && alr --version
+            command -v gnat >/dev/null && gnat --version | head -n1
+            command -v gprbuild >/dev/null && gprbuild --version | head -n1
+          '';
+        };
+      }
+    );
+}