Fix clippy warnings.

This commit fixes the current set of (stable) clippy warnings in the repo.

cranelift/codegen/src/lib.rs

@@ -18,13 +18,12 @@
                 clippy::assign_op_pattern,
                 clippy::empty_line_after_outer_attr,
 // Hard to avoid in generated code:
-                clippy::cyclomatic_complexity,
+                clippy::cognitive_complexity,
                 clippy::too_many_arguments,
 // Code generator doesn't have a way to collapse identical arms:
                 clippy::match_same_arms,
 // These are relatively minor style issues, but would be easy to fix:
                 clippy::new_without_default,
-                clippy::new_without_default_derive,
                 clippy::should_implement_trait,
                 clippy::len_without_is_empty))]
 #![cfg_attr(
@@ -35,7 +34,6 @@
         clippy::nonminimal_bool,
         clippy::option_map_unwrap_or,
         clippy::option_map_unwrap_or_else,
-        clippy::print_allocout,
         clippy::unicode_not_nfc,
         clippy::use_self
     )