From fe800447c27f66ef73bd82823dde3dca8448bd9a Mon Sep 17 00:00:00 2001
From: Thomas Tuegel <ttuegel@mailbox.org>
Date: Fri, 21 Jul 2017 11:39:50 -0500
Subject: [PATCH] qemu: unset CPP

Commit 093cc00cdd9d8cf31ecce5bc1dd3645c460a1b98 sets the environment variable
`CPP' by default, but this interferes with dependency calculation.
---
 pkgs/applications/virtualization/qemu/default.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkgs/applications/virtualization/qemu/default.nix b/pkgs/applications/virtualization/qemu/default.nix
index d09926da7cdb..8277261a1500 100644
--- a/pkgs/applications/virtualization/qemu/default.nix
+++ b/pkgs/applications/virtualization/qemu/default.nix
@@ -59,6 +59,10 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "stackprotector" ];
 
+  preConfigure = ''
+    unset CPP # intereferes with dependency calculation
+  '';
+
   configureFlags =
     [ "--smbd=smbd" # use `smbd' from $PATH
       "--audio-drv-list=${audio}"