haskellSrc2nix: disallow substitutes

Fix #49818. See the bug for more details.

The work done by haskellSrc2nix is usually lightweight, but needs to
be done each time a cabal file change. This triggers unexpected
network activity for a cache query which results most of the time on a
cache miss.

By disabling substitutes we:

- avoid the, mostly useless, binary cache query
- avoid unexpected network failure when users change a cabal file and
  try to rebuild without connectivity.

1 files changed, 1 insertions, 0 deletions

diff --git a/pkgs/development/haskell-modules/make-package-set.nix b/pkgs/development/haskell-modules/make-package-set.nix
index 5803e2946bff..e36933a81944 100644
--- a/pkgs/development/haskell-modules/make-package-set.nix
+++ b/pkgs/development/haskell-modules/make-package-set.nix
@@ -125,6 +125,7 @@ let
       name = "cabal2nix-${name}";
       nativeBuildInputs = [ pkgs.buildPackages.cabal2nix ];
       preferLocalBuild = true;
+      allowSubstitutes = false;
       phases = ["installPhase"];
       LANG = "en_US.UTF-8";
       LOCALE_ARCHIVE = pkgs.lib.optionalString (buildPlatform.libc == "glibc") "${buildPackages.glibcLocales}/lib/locale/locale-archive";