Corrects condition to compile out MSVC's pragmas. This fixes the build on MinGW.

include/gmock/gmock-matchers.h

@@ -1392,15 +1392,15 @@ class TrulyMatcher {
   template <typename T>
   bool MatchAndExplain(T& x,  // NOLINT
                        MatchResultListener* /* listener */) const {
-#if GTEST_OS_WINDOWS
+#if _MSC_VER
     // MSVC warns about converting a value into bool (warning 4800).
 # pragma warning(push)          // Saves the current warning state.
 # pragma warning(disable:4800)  // Temporarily disables warning 4800.
-#endif  // GTEST_OS_WINDOWS
+#endif
     return predicate_(x);
-#if GTEST_OS_WINDOWS
+#if _MSC_VER
 # pragma warning(pop)           // Restores the warning state.
-#endif  // GTEST_OS_WINDOWS
+#endif
   }
 
   void DescribeTo(::std::ostream* os) const {