--fix fails sometimes if clippy and sccache used: "error: Unrecognized option: \'E\'\n\n

[matthiaskrgr]

https://github.com/rust-random/rand
When checking the rand crate for example with cargo clippy -Zunstable-options --fix while using sccache-git, the following error is thrown:

    Checking ppv-lite86 v0.2.6
    Checking rand_core v0.5.1 (/home/matthias/vcs/github/rand/rand_core)
error: failed to execute compile
caused by: Compiler not supported: "error: Unrecognized option: \'E\'\n\n"
error: could not compile `rand_core`.

To learn more, run the command again with --verbose.

The strange thing is that -E is never passed according to --verbose.

Discord logs of when we tried to find out what is going on:
https://discordapp.com/channels/442252698964721669/459149871191031810/701833971608059906

[phansch]

@matthiaskrgr I believe this can be closed with mozilla/sccache#728 being merged?

[matthiaskrgr]

Right, I forgot to check back on that.