Check test the driver and adapter handle OsStrings correctly

[xFrednet]

Lint crates are compiled by cargo-marker, the path of the build binary is passed to the adapter via environment values. The loading of these libraries should ideally use OsString to ensure that it works with whatever interesting path a user might throw at it. This requires a bit of auditing.

cargo-marker has been checked as part of #66 and should be fine. A second pair of eyes would be appreciated :)