build: linking Carbon framework for OSX

Even though libuv has no link time dependencies, linking Carbon for OSX
is needed for OSX debugging features to function properly.

This commit undoes https://github.com/joyent/node/commit/358c2901567c005689dceef1361754cca95ca14e.

### Without linking Carbon

![screen shot 2014-08-06 at 2 04 45 pm](https://cloud.githubusercontent.com/assets/192891/3831583/06b41f38-1d95-11e4-990e-6a4241fe7fd6.png)

### Linking Carbon

![screen shot 2014-08-06 at 2 05 49 pm](https://cloud.githubusercontent.com/assets/192891/3831588/10a3e3d4-1d95-11e4-8e32-2732972cb999.png)