rustfmt: wrap cargo-fmt with cargo (#291578)

pkgs/development/compilers/rust/rustfmt.nix

@@ -1,6 +1,14 @@
-{ lib, stdenv, rustPlatform, rustc, Security, asNightly ? false }:
+{ lib
+, stdenv
+, cargo
+, makeWrapper
+, rustPlatform
+, rustc
+, Security
+, asNightly ? false
+}:
 
-rustPlatform.buildRustPackage rec {
+rustPlatform.buildRustPackage {
   pname = "rustfmt" + lib.optionalString asNightly "-nightly";
   inherit (rustc) version src;
 
@@ -11,6 +19,10 @@ rustPlatform.buildRustPackage rec {
   # changes hash of vendor directory otherwise
   dontUpdateAutotoolsGnuConfigScripts = true;
 
+  nativeBuildInputs = [
+    makeWrapper
+  ];
+
   buildInputs = [
     rustc.llvm
   ] ++ lib.optional stdenv.hostPlatform.isDarwin Security;
@@ -34,6 +46,11 @@ rustPlatform.buildRustPackage rec {
   CFG_RELEASE = rustc.version;
   CFG_RELEASE_CHANNEL = if asNightly then "nightly" else "stable";
 
+  postInstall = ''
+    wrapProgram $out/bin/cargo-fmt \
+      --suffix PATH : ${lib.makeBinPath [ cargo ]}
+  '';
+
   meta = with lib; {
     description = "Tool for formatting Rust code according to style guidelines";
     homepage = "https://github.com/rust-lang-nursery/rustfmt";