Fix Win64 build

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index d40bc6750bdc29970a88222f620d9be3bdd18056..c339781d26597ff5ec2270b229ba1601dfe0c90b 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -9,6 +9,8 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
+#ifndef _WIN64
+
 // Adds X64-specific methods for generating operands.
 class X64OperandGenerator V8_FINAL : public OperandGenerator {
  public:
@@ -677,6 +679,8 @@ void InstructionSelector::VisitCall(Node* call, BasicBlock* continuation,
   }
 }
 
+#endif
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8