nix: Fix gpu-lib/wayland binary patching on nix package (#16958)

Also, includes some cleanup -- adds missing flake-compat input and
aligns the nix build module with how nixpkgs does it.

Release Notes:

- Fixed an issue on NixOS package where the wrong binaries were being
patched, leading to missing Wayland libs when launching Zed

flake.nix

@@ -11,7 +11,7 @@
       url = "github:ipetkov/crane";
       inputs.nixpkgs.follows = "nixpkgs";
     };
-
+    flake-compat.url = "github:edolstra/flake-compat";
   };
 
   outputs = {
@@ -32,8 +32,11 @@
   in {
     packages = forAllSystems (pkgs: let
       craneLib = (crane.mkLib pkgs).overrideToolchain (p: p.fenix.stable.toolchain);
+      rustPlatform = pkgs.makeRustPlatform {
+        inherit (pkgs.fenix.stable.toolchain) cargo rustc;
+      };
       nightlyBuild = pkgs.callPackage ./nix/build.nix {
-        inherit craneLib;
+        inherit craneLib rustPlatform;
       };
     in {
       zed-editor = nightlyBuild;
@@ -46,9 +49,12 @@
 
     formatter = forAllSystems (pkgs: pkgs.alejandra);
 
-    overlays.default = final: _prev: {
+    overlays.default = final: prev: {
       zed-editor = final.callPackage ./nix/build.nix {
         craneLib = (crane.mkLib final).overrideToolchain (p: p.fenix.stable.toolchain);
+        rustPlatform = final.makeRustPlatform {
+          inherit (final.fenix.stable.toolchain) cargo rustc;
+        };
       };
     };
   };