Fixing MinGW build.

BUG=v8:1695

Review URL: http://codereview.chromium.org/8081015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9488 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/d8.cc

@@ -817,7 +817,7 @@ void Shell::OnExit() {
 
 
 static FILE* FOpen(const char* path, const char* mode) {
-#if (defined(_WIN32) || defined(_WIN64))
+#if defined(_MSC_VER) && (defined(_WIN32) || defined(_WIN64))
   FILE* result;
   if (fopen_s(&result, path, mode) == 0) {
     return result;