qt5.qtlocation: fix build on Darwin

Well, "fix", because this just allows us to use deprecated C++ features
for now, and the actual consumer of said features is boost 1.65.1,
vendored inside mapbox-gl, vendored inside qtlocation, with all the
upstreams in this chain being mostly dead.

Anyway, this should buy us time until the next libcxx bump comes around,
and then we'll have to send qt5location to a farm upstate unless someone
wants to go through the entire boost codebase and precision-upgrade it.

pkgs/development/libraries/qt-5/modules/qtlocation.nix

@@ -9,5 +9,6 @@ qtModule {
      # This flag re-enables this feature
      # https://libcxx.llvm.org/docs/UsingLibcxx.html#c-17-specific-configuration-macros
      "QMAKE_CXXFLAGS+=-D_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR"
+     "QMAKE_CXXFLAGS+=-D_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION"
   ];
 }