Bug 411511 - fixed mingw build. r=bsmedberg

--HG--
extra : rebase_source : 300ed0758f4abdf5bf4f2d151bdb3bb4e4e5e2d4

xpcom/tests/TestUnicodeArguments.cpp

@@ -4,7 +4,7 @@
  */
 
 static const int args_length = 4;
-#ifdef XP_WIN
+#if defined(XP_WIN) && defined(_MSC_VER)
 #define _UNICODE
 #include <tchar.h>
 #include <stdio.h>