no_std fixes.

lib/execute/src/instance_plus.rs

@@ -5,6 +5,7 @@ use cranelift_wasm::DefinedFuncIndex;
 use jit_code::JITCode;
 use link::link_module;
 use resolver::Resolver;
+use std::boxed::Box;
 use std::cmp::max;
 use std::rc::Rc;
 use std::slice;

lib/execute/src/lib.rs

@@ -53,7 +53,7 @@ pub use resolver::{NullResolver, Resolver};
 
 #[cfg(not(feature = "std"))]
 mod std {
-    pub use alloc::{string, vec};
+    pub use alloc::{boxed, rc, string, vec};
     pub use core::*;
     pub use core::{i32, str, u32};
 }

lib/execute/src/trampoline_park.rs

@@ -6,6 +6,7 @@ use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use jit_code::JITCode;
 use std::collections::HashMap;
 use std::fmt;
+use std::vec::Vec;
 use wasmtime_environ::{CompileError, RelocSink};
 use wasmtime_runtime::{InstantiationError, VMFunctionBody};