Incoming clippy breakage

[phansch]

rust-lang/rust#50615 renames rustc_trans to rustc_codegen, which we use in src/driver.rs#L12

[witchof0x20]

Would a PR for this be welcome? I wrote up this commit which is pretty much identical to rust-lang/rls#872

[oli-obk]

Fixed in #2775

@witchof0x20 someone got ahead of you. please don't hesitate to open PRs. We're very happy about any contributions! Even if something is not a full fix or impl, just open a PR, we can figure out the details afterwards