From 4e7c3b982831bc209072fc0a31cd3e11f9ac7b56 Mon Sep 17 00:00:00 2001
From: sternenseemann <sternenseemann@systemli.org>
Date: Thu, 4 Aug 2022 15:15:55 +0200
Subject: [PATCH] haskell.compiler.ghc941: apply fix for racy build system

https://gitlab.haskell.org/ghc/ghc/-/merge_requests/8751
https://gitlab.haskell.org/ghc/ghc/-/issues/21934

Hopefully this patch fixes the problem we experienced on Hydra once (out
of three builds).
---
 pkgs/development/compilers/ghc/9.4.1.nix | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pkgs/development/compilers/ghc/9.4.1.nix b/pkgs/development/compilers/ghc/9.4.1.nix
index f883796452c8..e24f9fbb3767 100644
--- a/pkgs/development/compilers/ghc/9.4.1.nix
+++ b/pkgs/development/compilers/ghc/9.4.1.nix
@@ -197,6 +197,12 @@ stdenv.mkDerivation (rec {
       extraPrefix = "utils/haddock/";
       stripLen = 1;
     })
+    # fix race condition in make build system
+    (fetchpatch {
+      name = "ghc-hs-boot-copying-fix.patch";
+      url = "https://gitlab.haskell.org/ghc/ghc/-/commit/4f17eff0cbd125eca55b68f4927befdd45008eb6.diff";
+      sha256 = "0anq3w9z9mhxb0wx6rvxac3n7rl3apcma9zk3r9zz9hj9v7vkqzx";
+    })
   ];
 
   postPatch = "patchShebangs .";