bento4: fix build on darwin (#314361)

CMakeLists.txt in v1.6.0-641 set `CMAKE_OSX_ARCHITECTURES`, which broke
evaluation on Darwin. Fix it by unsetting `CMAKE_OSX_ARCHITECTURES`.

Author: al3xtjames

pkgs/tools/video/bento4/default.nix

@@ -18,7 +18,11 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake ];
 
-  cmakeFlags = [ "-DBUILD_SHARED_LIBS=ON" ];
+  cmakeFlags = [
+    "-DBUILD_SHARED_LIBS=ON"
+  ] ++ lib.optionals stdenv.isDarwin [
+    "-DCMAKE_OSX_ARCHITECTURES="
+  ];
 
   installPhase = ''
     runHook preInstall