writers: run fixupPhase for darwin bin writers

mach-o executables we produce in writers are not always fully valid for
some reason. In normal derivation this is fixed in fixupPhase and we can
replicate this behavior here easily.

Resolves #132660.

pkgs/build-support/writers/default.nix

@@ -78,6 +78,10 @@ rec {
       ${compileScript}
       ${lib.optionalString strip
           "${lib.getBin buildPackages.bintools-unwrapped}/bin/${buildPackages.bintools-unwrapped.targetPrefix}strip -S $out"}
+      # Sometimes binaries produced for darwin (e. g. by GHC) won't be valid
+      # mach-o executables from the get-go, but need to be corrected somehow
+      # which is done by fixupPhase.
+      ${lib.optionalString pkgs.stdenvNoCC.hostPlatform.isDarwin "fixupPhase"}
       ${optionalString (types.path.check nameOrPath) ''
         mv $out tmp
         mkdir -p $out/$(dirname "${nameOrPath}")

pkgs/top-level/release-haskell.nix

@@ -330,10 +330,7 @@ let
         };
         constituents = accumulateDerivations [
           # haskell specific tests
-          #
-          # TODO: The writers test appears to be failing on darwin for unknown
-          # reasons.  See https://github.com/NixOS/nixpkgs/pull/129606#issuecomment-881307871.
-          (lib.recursiveUpdate jobs.tests.haskell { writers.x86_64-darwin = null; })
+          jobs.tests.haskell
           # important top-level packages
           jobs.cabal-install
           jobs.cabal2nix