Inverted the condition for clarity

Author: derekmauro

src/time_zone_format.cc

@@ -13,10 +13,10 @@
 //   limitations under the License.
 
 #if !defined(HAS_STRPTIME)
-# if !defined(_MSC_VER) && !defined(__MINGW32__) && !defined(__VXWORKS__)
-#  define HAS_STRPTIME 1  // Assume everyone else has strptime().
-# else
+# if defined(_MSC_VER) || defined(__MINGW32__) || defined(__VXWORKS__)
 #  define HAS_STRPTIME 0
+# else
+#  define HAS_STRPTIME 1  // Assume everyone else has strptime().
 # endif
 #endif