z3_4_4_0: Fix build on darwin.

pkgs/applications/science/logic/z3/4.4.0.nix

@@ -14,6 +14,8 @@ stdenv.mkDerivation rec {
   buildInputs = [ python ];
   enableParallelBuilding = true;
 
+  CXXFLAGS = if stdenv.isDarwin then "-std=gnu++98" else null;
+
   configurePhase = "python scripts/mk_make.py --prefix=$out && cd build";
 
   # z3's install phase is stupid because it tries to calculate the

pkgs/top-level/all-packages.nix

@@ -33631,7 +33631,7 @@ with pkgs;
   z3 = z3_4_8;
   z3_4_4_0 = callPackage ../applications/science/logic/z3/4.4.0.nix {
     python = python2;
-    stdenv = gcc49Stdenv;
+    stdenv = if stdenv.isDarwin then stdenv else gcc49Stdenv;
   };
   z3-tptp = callPackage ../applications/science/logic/z3/tptp.nix {};