Need to use MakeByRefType to avoid problems with GC #1190
Description
See dotnet/coreclr#18865
cc @xPaw
unbox of a struct produces a managed pointer (type &) so the local here needs to be declared as a ByRef. Otherwise the jit won't track the pointer and report it to GC, leading to eventual badness when GC moves things.
- il.DeclareLocal(type.MakePointerType());
+ il.DeclareLocal(type.MakeByRefType());