Fix check for V8_TARGET_OS_WIN macro

On Windows with MSVC, the current code triggers a fatal error C1017
(invalid integer constant expression).

Change-Id: I41c371a1d7909737052c03c830bb62c41154a192
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1871918
Commit-Queue: Michaël Zasso <mic.besace@gmail.com>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64418}

src/codegen/turbo-assembler.h

@@ -102,7 +102,7 @@ class V8_EXPORT_PRIVATE TurboAssemblerBase : public Assembler {
   static bool IsAddressableThroughRootRegister(
       Isolate* isolate, const ExternalReference& reference);
 
-#if V8_TARGET_OS_WIN
+#ifdef V8_TARGET_OS_WIN
   // Minimum page size. We must touch memory once per page when expanding the
   // stack, to avoid access violations.
   static constexpr int kStackPageSize = 4 * KB;