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

nix/build.nix

@@ -1,6 +1,7 @@
 {
   lib,
   craneLib,
+  rustPlatform,
   clang,
   llvmPackages_18,
   mold-wrapped,
@@ -48,6 +49,17 @@
     // {
       inherit src stdenv;
 
+      nativeBuildInputs = [
+        clang
+        copyDesktopItems
+        curl
+        mold-wrapped
+        perl
+        pkg-config
+        protobuf
+        rustPlatform.bindgenHook
+      ];
+
       buildInputs = [
         curl
         fontconfig
@@ -57,22 +69,13 @@
         sqlite
         zlib
         zstd
+
         alsa-lib
         libxkbcommon
         wayland
         xorg.libxcb
       ];
 
-      nativeBuildInputs = [
-        clang
-        copyDesktopItems
-        curl
-        mold-wrapped
-        perl
-        pkg-config
-        protobuf
-      ];
-
       ZSTD_SYS_USE_PKG_CONFIG = true;
       FONTCONFIG_FILE = makeFontsConf {
         fontDirectories = [
@@ -103,8 +106,8 @@
         else "";
 
       postFixup = ''
-        patchelf --add-rpath ${gpu-lib}/lib $out/bin/*
-        patchelf --add-rpath ${wayland}/lib $out/bin/*
+        patchelf --add-rpath ${gpu-lib}/lib $out/libexec/*
+        patchelf --add-rpath ${wayland}/lib $out/libexec/*
       '';
 
       postInstall = ''