It seems due to a so far possibly unfiled bug, cargo fails to
get it's CWDs right.
Last verified with cargo 0.11.0-nightly (42bce5c 2016-05-17).
To reproduce, just put the deleted file back and run a build command,
such as
```bash
make drive3-cli-cargo ARGS=build --no-default-features --features=nightly
```
Fixes#149
This allows to build everything concurrently without failure provided
the latest cargo is used.
https://github.com/rust-lang/cargo/pull/1764
It's still very early in development, but works for me nevertheless.
[skip ci]
Starting from cargo 0.3.0, one can override the target-directory
to be an absolute path, forcing all output to be dumped into
one and the same target dir.
That way, all dependencies are shared among the projects, saving
4 to 7 minutes per project in debug and release mode respectively.
