Flush output stream in wxMessageOutputStderr::Output() to avoid losing any output if the program crashes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61460 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/msgout.cpp

@@ -147,6 +147,8 @@ void wxMessageOutputStderr::Output(const wxString& str)
         fprintf(m_fp, "%s", (const char*) buf);
     else // print at least something
         fprintf(m_fp, "%s", (const char*) strWithLF.ToAscii());
+
+    fflush(m_fp);
 }
 
 // ----------------------------------------------------------------------------