Update setuptools (3.4.3 -> 3.4.4)
Fix `fetch_git` with `--keep`

Update existing git repo if exists, or clone if not exists.
The destination repo might exist if the `--keep` was supplied for `python-build`.
*EXPERIMENTAL* Add https://github.com/dropbox/pyston
Specify `GCC_CONFIGURE_OPTS`
Suppress the error output from `gcc --version`
Update git working copy