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/src/wasm.rs

@@ -90,10 +90,6 @@ pub struct Options {
     /// Specify an input file to be used. Use '-' for stdin.
     files: Vec<PathBuf>,
 
-    /// Enable debug output on stderr/stdout
-    #[clap(short)]
-    debug: bool,
-
     /// Print bytecode size
     #[clap(short = 'X')]
     print_size: bool,
@@ -137,8 +133,6 @@ impl std::str::FromStr for ColorOpt {
 }
 
 pub fn run(options: &Options) -> Result<()> {
-    crate::handle_debug_flag(options.debug);
-
     let parsed = parse_sets_and_triple(&options.settings, &options.target)?;
     for path in &options.files {
         let name = String::from(path.as_os_str().to_string_lossy());