Add support for NixOS

Additionally - fix some shellcheck warnings in repack.sh

Change-Id: I2cbc6516c54a4f4e4ecef817ed9fe90b0a460faa

flake.nix

@@ -0,0 +1,35 @@
+{
+  description = "Native Yandex Music desktop client";
+  inputs = {
+    ymExe = {
+      url = https://music-desktop-application.s3.yandex.net/stable/Yandex_Music_x64_5.0.6.exe;
+      flake = false;
+    };
+  };
+  outputs = { self, ymExe, nixpkgs, flake-utils }:
+    let
+      yandex_music_with = pkgs: pkgs.callPackage ./. {
+        inherit ymExe;
+      };
+    in
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+        in
+        {
+          packages = rec {
+            yandex_music = yandex_music_with pkgs;
+            default = yandex_music;
+          };
+        }
+      ) // {
+      modules = [{
+        nixpkgs.overlays = [
+          (final: prev: {
+            yandex_music = yandex_music_with prev;
+          })
+        ];
+      }];
+    };
+}