Problem

I added build.rustc-wrapper = "sccache" to use the sccache in my builds, but when running any cargo command, it says that build.rustc-wrapper is an unused key.
I found the key in The Cargo Book (https://doc.rust-lang.org/cargo/guide/build-cache.html).

Steps

1. Install sccache cargo install sccache
2. Add build.rustc-wrapper = "sccache" to Cargo config ($CARGO_HOME/config)
3. Run cargo build in any project

Notes

Output of cargo version: cargo 1.40.0 (bc8e4c8 2019-11-22)

Rust version: 1.40.0
OS: Windows 10