This was being overriden by `lf=eof` in `.gitattributes` in the root
directory. Override it again to avoid warnings like this:
```
$ git diff src/tools/rustfmt/tests/target/issue-3494/crlf.rs
warning: CRLF will be replaced by LF in src/tools/rustfmt/tests/target/issue-3494/crlf.rs.
The file will have its original line endings in your working directory
```
