Yes, that fails. I'm not an expert, but I make the assumtion that on 10.9 we want to compile with libc++. Using the `--use-system-boost` as a scons argument seems to require this, since boost will have been built with libc++.

If we omit `osx-version-min`, it defaults to 10.6 (in the mongodb SConscript), which does not work together with `libc++`.

If we do not pass `--libc++` to scons, we need to pass `--osx-version-min=10.9`, else the build defaults to `libstdc++`. Using `libstdc++` compiles, but makes the resulting `*.a` library not so useful (on mavericks).

If we do pass `--libc++` we need to pass `osx-version-min` >= 10.7 for it to compile. I think on Mavericks we should simply pass this combination of flags.