README: Add subsection on running Clippy as a rustc wrapper

This is useful for projects that do not use cargo.

Signed-off-by: Miguel Ojeda <[email protected]>

Author: ojeda

README.md

@@ -98,6 +98,26 @@ If you want to run Clippy **only** on the given crate, use the `--no-deps` optio
 cargo clippy -p example -- --no-deps 
 ```
 
+### As a rustc replacement (`clippy-driver`)
+
+Clippy can also be used in projects that do not use cargo. To do so, you will need to replace
+your `rustc` compilation commands with `clippy-driver`. For example, if your project runs:
+
+```terminal
+rustc --edition 2018 -Cpanic=abort foo.rs
+```
+
+Then, to enable Clippy, you will need to call:
+
+```terminal
+clippy-driver --edition 2018 -Cpanic=abort foo.rs
+```
+
+Note that `rustc` will still run, i.e. it will still emit the output files it normally does.
+
+You may notice that keeping `rustc` as the second argument (i.e. wrapping `rustc` by prepending
+`clippy-driver`) also works; however, the preferred way is to *not* wrap it.
+
 ### Travis CI
 
 You can add Clippy to Travis CI in the same way you use it locally: