cranelift_wasm: expose the original Wasm function signature

In the `ModuleEnvironment::declare_signature` callback, also pass the original
Wasm function signature, so that consumers may associate this information with
each compiled function. This is often necessary because while each Wasm
signature gets compiled down into a single native signature, multiple Wasm
signatures might compile down into the same native signature, and in these cases
the original Wasm signature is required for dynamic type checking of calls.

cranelift/wasm/src/environ/dummy.rs

@@ -6,7 +6,8 @@
 //! [Wasmtime]: https://github.com/bytecodealliance/wasmtime
 
 use crate::environ::{
-    FuncEnvironment, GlobalVariable, ModuleEnvironment, ReturnMode, TargetEnvironment, WasmResult,
+    FuncEnvironment, GlobalVariable, ModuleEnvironment, ReturnMode, TargetEnvironment,
+    WasmFuncType, WasmResult,
 };
 use crate::func_translator::FuncTranslator;
 use crate::state::ModuleTranslationState;
@@ -534,7 +535,7 @@ impl TargetEnvironment for DummyEnvironment {
 }
 
 impl<'data> ModuleEnvironment<'data> for DummyEnvironment {
-    fn declare_signature(&mut self, sig: ir::Signature) -> WasmResult<()> {
+    fn declare_signature(&mut self, _wasm: &WasmFuncType, sig: ir::Signature) -> WasmResult<()> {
         self.info.signatures.push(sig);
         Ok(())
     }