rustfmt messages usually starts with line similar to this:

Diff in /home/runner/some/random/path.rs at line 135:

We could probably add the problem matcher similar to rust one to highlight them, so it would be easier to read logs.

Thing to check: would it be possible to "enable" this matcher only if `cargo f

This command maybe used to determine the path to some internal files (i.e. to link compiler-rt builtins for ubsan), but when used with dist-clang the client outputs only a filename as a first line. The client should output only a single line provided by real compiler.