Add -std:c++17 flag on test windows build

test/SConstruct

@@ -104,6 +104,7 @@ elif env['platform'] == "windows":
 
     env.Append(CPPDEFINES=['WIN32', '_WIN32', '_WINDOWS', '_CRT_SECURE_NO_WARNINGS'])
     env.Append(CCFLAGS=['-W3', '-GR'])
+    env.Append(CXXFLAGS=['-std:c++17'])
     if env['target'] in ('debug', 'd'):
         env.Append(CPPDEFINES=['_DEBUG'])
         env.Append(CCFLAGS=['-EHsc', '-MDd', '-ZI'])