Dongsu Park 276137505e eclass: clean up .crates2.json when running cargo install ...

When instaling rust packages with Rust 1.42, it fails like the
following message:

```
 * Detected file collision(s):
 *
 *      /build/amd64-usr/usr/.crates2.json
```

Fix the install function in cargo.eclass so it can clean up the garbage
json file.

2020-03-19 11:43:13 +01:00

..

src/third_party/portage-stable

eclass: clean up .crates2.json when running cargo install

2020-03-19 11:43:13 +01:00