From 0e1dfe702d28df2842aef1c9b8e83a36d4fe1b54 Mon Sep 17 00:00:00 2001
From: Peter Simons <simons@cryp.to>
Date: Thu, 28 Mar 2013 12:58:10 +0100
Subject: [PATCH] pkgs/build-support/cabal: strip unnecessary --extra-lib-dir
 arguments for haskell packages

Packages that are registered in the ghc-pkg database don't need any
extra flags passed for Cabal to recognize them.
---
 pkgs/build-support/cabal/default.nix | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pkgs/build-support/cabal/default.nix b/pkgs/build-support/cabal/default.nix
index 765beceb2a4..6d615e1d0c8 100644
--- a/pkgs/build-support/cabal/default.nix
+++ b/pkgs/build-support/cabal/default.nix
@@ -115,7 +115,9 @@
                 fi
                 for d in lib{,64}; do
                   if [ -d "$p/$d" ]; then
-                    extraConfigureFlags+=" --extra-lib-dir=$p/$d"
+                    if [ ! -d "$p/$d/ghc-pkgs" ]; then
+                      extraConfigureFlags+=" --extra-lib-dir=$p/$d"
+                    fi
                   fi
                 done
               done