clif-util: always use pretty-env-logger (#4443)

Rather than sometimes using `file-per-thread-logger`.

Also remove the debug CLI flags, so that we can always just define
`RUST_LOG=...` to get logging and don't need to also do other things.

cranelift/Cargo.toml

@@ -36,7 +36,6 @@ wat = { version = "1.0.45", optional = true }
 target-lexicon = { version = "0.12", features = ["std"] }
 pretty_env_logger = "0.4.0"
 rayon = { version = "1", optional = true }
-file-per-thread-logger = "0.1.2"
 indicatif = "0.13.0"
 thiserror = "1.0.15"
 walkdir = "2.2"