Martin Donlon 95de3e9fea Add support for [env] section in .cargo/config.toml
This adds support for an `[env]` section in the config.toml files. Environment variables set in this section will be applied to the environment of any processes executed by cargo.

```
[env]
FOOBAR = "Apple"
PATH_TO_SOME_TOOL = { value = "bin/tool", relative = true }
USERNAME = { value = "test_user", force = true }
```
2021-02-15 15:17:00 -08:00
..
2020-08-10 11:29:28 -07:00