From d8dd3014120af31d4567de8247900a1088ec6e7b Mon Sep 17 00:00:00 2001
From: John Ericson <git@JohnEricson.me>
Date: Wed, 25 Dec 2019 14:34:40 -0500
Subject: [PATCH] haskell generic-builder: Hack so CPP without a CC works

---
 pkgs/development/haskell-modules/generic-builder.nix | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/haskell-modules/generic-builder.nix b/pkgs/development/haskell-modules/generic-builder.nix
index e27769d9c766..018979cf7aed 100644
--- a/pkgs/development/haskell-modules/generic-builder.nix
+++ b/pkgs/development/haskell-modules/generic-builder.nix
@@ -133,8 +133,11 @@ let
   crossCabalFlags = [
     "--with-ghc=${ghcCommand}"
     "--with-ghc-pkg=${ghc.targetPrefix}ghc-pkg"
+    # Pass the "wrong" C compiler rather than none at all so packages that just
+    # use the C preproccessor still work, see
+    # https://github.com/haskell/cabal/issues/6466 for details.
+    "--with-gcc=${(if stdenv.hasCC then stdenv else buildPackages.stdenv).cc.targetPrefix}cc"
   ] ++ optionals stdenv.hasCC [
-    "--with-gcc=${stdenv.cc.targetPrefix}cc"
     "--with-ld=${stdenv.cc.bintools.targetPrefix}ld"
     "--with-ar=${stdenv.cc.bintools.targetPrefix}ar"
     # use the one that comes with the cross compiler.