vampire: allow custom z3 version to be overridden

pkgs/by-name/va/vampire/package.nix

@@ -4,10 +4,7 @@
   fetchFromGitHub,
   cmake,
   z3,
-}:
-
-let
-  z3_4_14_0 = z3.overrideAttrs rec {
+  z3' ? z3.overrideAttrs rec {
     version = "4.14.0";
     src = fetchFromGitHub {
       owner = "Z3Prover";
@@ -15,8 +12,8 @@ let
       rev = "z3-${version}";
       hash = "sha256-Bv7+0J7ilJNFM5feYJqDpYsOjj7h7t1Bx/4OIar43EI=";
     };
-  };
-in
+  },
+}:
 stdenv.mkDerivation (finalAttrs: {
   pname = "vampire";
   version = "5.0.1";
@@ -31,10 +28,10 @@ stdenv.mkDerivation (finalAttrs: {
 
   nativeBuildInputs = [ cmake ];
   buildInputs = [
-    z3_4_14_0
+    z3'
   ];
 
-  cmakeFlags = [ (lib.cmakeFeature "Z3_DIR" "${z3_4_14_0.dev}/lib/cmake") ];
+  cmakeFlags = [ (lib.cmakeFeature "Z3_DIR" "${z3'.dev}/lib/cmake") ];
 
   enableParallelBuilding = true;