don't run vsnprintf() test if we're using the system version, there is nothing we can do about its failures then anyhow

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@53857 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/strings/vsnprintf.cpp

@@ -19,6 +19,8 @@
     #pragma hdrstop
 #endif
 
+#if wxUSE_WXVSNPRINTF
+
 #ifndef WX_PRECOMP
     #include "wx/wx.h"
     #include "wx/wxchar.h"
@@ -549,3 +551,5 @@ void VsnprintfTestCase::Miscellaneous()
     DoMisc(5, wxT("%%%%%"), 6,  wxT("%%%%%%%%%%"));
     DoMisc(6, wxT("%%%%12"), 7,  wxT("%%%%%%%%%d"), 12);
 }
+
+#endif // wxUSE_WXVSNPRINTF