nix: Propagate doCheck argument through nix files.

release.nix

@@ -1,10 +1,12 b''
 { pkgs ? import <nixpkgs> {}
+, doCheck ? true
 }:
 
 let
 
   vcsserver = import ./default.nix {
     inherit
+      doCheck
       pkgs;
   };
 

shell.nix

@@ -1,8 +1,13 b''
-{ pkgs ? (import <nixpkgs> {})
+{ pkgs ? import <nixpkgs> {}
+,  doCheck ? false
 }:
 
 let
-  vcsserver = import ./default.nix {inherit pkgs;};
+  vcsserver = import ./default.nix {
+    inherit
+      doCheck
+      pkgs;
+  };
 
 in vcsserver.override (attrs: {