compiler: fix incorrect DWARF type in some generic parameters

For some reason, the type of a function parameter can sometimes be of
interface type, while it should be the underlying type. This might be a
bug in the x/tools/go/ssa package but this is a simple workaround.

compiler/compiler.go

@@ -688,7 +688,7 @@ func (b *builder) getLocalVariable(variable *types.Var) llvm.Metadata {
 				Name:           param.Name(),
 				File:           b.getDIFile(pos.Filename),
 				Line:           pos.Line,
-				Type:           b.getDIType(variable.Type()),
+				Type:           b.getDIType(param.Type()),
 				AlwaysPreserve: true,
 				ArgNo:          i + 1,
 			})