update model to modular structure

system-environment/config.nix

@@ -0,0 +1,27 @@
+{ pkgs, ... }:
+{
+    environment.systemPackages = with pkgs; [
+        # Make systems
+        gnumake
+        cmake
+        cmakeCurses
+
+        # C/C++/Fortran tools
+        gcc
+        clang
+
+        # Common C based dependencies
+        eigen
+
+        # Ada/+Spark & Rust tools
+        alire
+        gnat
+        rustc
+        cargo
+    ];
+
+    environment.variables = {
+    };
+
+
+}