rustc: remove test-only git dependency

The tests have been disabled for over a year,
and AFAIK `git` was added and is only used for the rustc tests.

pkgs/development/compilers/rust/rustc.nix

@@ -1,6 +1,6 @@
 { stdenv, removeReferencesTo, pkgsBuildBuild, pkgsBuildHost, pkgsBuildTarget
 , fetchurl, file, python3
-, llvm_9, darwin, git, cmake, rust, rustPlatform
+, llvm_9, darwin, cmake, rust, rustPlatform
 , pkgconfig, openssl
 , which, libffi
 , withBundledLLVM ? false
@@ -125,7 +125,7 @@ in stdenv.mkDerivation rec {
   dontUseCmakeConfigure = true;
 
   nativeBuildInputs = [
-    file python3 rustPlatform.rust.rustc git cmake
+    file python3 rustPlatform.rust.rustc cmake
     which libffi removeReferencesTo pkgconfig
   ];