Implement registering JIT unwind information on Windows.

This commit implements registering unwind information for JIT functions on
Windows so that the operating system can both walk and unwind stacks containing
JIT frames.

Currently this only works with Cranelift as lightbeam does not emit unwind
information yet.

This commit also resets the stack guard page on Windows for stack overflow
exceptions, allowing reliable stack overflow traps.

With these changes, all previously disabled test suite tests (not including
the multi-value tests) on Windows are now passing.

Fixes #291.

misc/wasmtime-py/src/import.rs

@@ -16,7 +16,7 @@ use cranelift_entity::{EntityRef, PrimaryMap};
 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
 use cranelift_wasm::{DefinedFuncIndex, FuncIndex};
 use target_lexicon::HOST;
-use wasmtime_environ::{Export, Module};
+use wasmtime_environ::{CompiledFunction, Export, Module};
 use wasmtime_jit::CodeMemory;
 use wasmtime_runtime::{Imports, InstanceHandle, VMContext, VMFunctionBody};
 
@@ -184,9 +184,16 @@ fn make_trampoline(
         )
         .expect("compile_and_emit");
 
+    let mut unwind_info = Vec::new();
+    context.emit_unwind_info(isa, &mut unwind_info);
+
     code_memory
-        .allocate_copy_of_byte_slice(&code_buf)
-        .expect("allocate_copy_of_byte_slice")
+        .allocate_for_function(&CompiledFunction {
+            body: code_buf,
+            jt_offsets: context.func.jt_offsets,
+            unwind_info,
+        })
+        .expect("allocate_for_function")
         .as_ptr()
 }