Nix: allow building from pure-eval mode (#2427)

* default.nix: allow import with pure-eval enabled

* Update hercules-ci/gitignore

* shell.nix: fix import of default.nix

nix/overlays/gitignore.nix

@@ -12,8 +12,8 @@ self: super:
       gitignoreSrc = super.fetchFromGitHub {
         owner = "hercules-ci";
         repo = "gitignore";
-        rev = "211907489e9f198594c0eb0ca9256a1949c9d412";
-        sha256 = "06j7wpvj54khw0z10fjyi31kpafkr6hi1k0di13k1xp8kywvfyx8";
+        rev = "a20de23b925fd8264fd7fad6454652e142fd7f73";
+        sha256 = "sha256-8DFJjXG8zqoONA1vXtgeKXy68KdJL5UaXR8NtVMUbx8=";
       };
     in
     (super.callPackage gitignoreSrc { }).gitignoreSource;

nix/static-haskell-package.nix

@@ -1,5 +1,5 @@
 # Derive a fully static Haskell package based on musl instead of glibc.
-{ nixpkgs, compiler, patches, allOverlays }:
+{ nixpkgs, system, compiler, patches, allOverlays }:
 
 name: src:
 let
@@ -46,7 +46,7 @@ let
 
   # Apply our overlay to nixpkgs.
   normalPkgs =
-    import nixpkgs { inherit overlays; };
+    import nixpkgs { inherit overlays system; };
 
   defaultCabalPackageVersionComingWithGhc =
     {