Fix some clippy warnings (#1277)

cranelift/codegen/src/isa/mod.rs

@@ -22,7 +22,6 @@
 //! ```
 //! # extern crate cranelift_codegen;
 //! # #[macro_use] extern crate target_lexicon;
-//! # fn main() {
 //! use cranelift_codegen::isa;
 //! use cranelift_codegen::settings::{self, Configurable};
 //! use std::str::FromStr;
@@ -40,7 +39,6 @@
 //!         let isa = isa_builder.finish(shared_flags);
 //!     }
 //! }
-//! # }
 //! ```
 //!
 //! The configured target ISA trait object is a `Box<TargetIsa>` which can be used for multiple

cranelift/codegen/src/isa/x86/abi.rs

@@ -938,7 +938,7 @@ fn insert_common_epilogue(
             .entry(fp_pop_inst)
             .and_modify(|insts| {
                 *insts = insts
-                    .into_iter()
+                    .iter()
                     .cloned()
                     .chain(std::iter::once(new_cfa))
                     .collect::<Box<[_]>>();