cmake: Removed Woverloaded-virtual from WARNING_C_FLAGS.
cmake: Removed Woverloaded-virtual from WARNING_C_FLAGS.

Because it is flag only for c++.

devMichaelJones/cpputest,bithium/cpputest,jaeguly/cpputest,Mindtribe/cpputest,chenlianbing/cpputest,jaeguly/cpputest,Mindtribe/cpputest,arstrube/cpputest,offa/cpputest,Mindtribe/cpputest,asgeroverby/cpputest,bithium/cpputest,dawid-aurobit/cpputest,asgeroverby/cpputest,dawid-aurobit/cpputest,maxilai/cpputest,arstrube/cpputest,dawid-aurobit/cpputest,cpputest/cpputest,KisImre/cpputest,KisImre/cpputest,cpputest/cpputest,basvodde/cpputest,arstrube/cpputest,PaulBussmann/cpputest,bithium/cpputest,jaeguly/cpputest,arstrube/cpputest,PaulBussmann/cpputest,asgeroverby/cpputest,chenlianbing/cpputest,offa/cpputest,KisImre/cpputest,dawid-aurobit/cpputest,jaeguly/cpputest,cpputest/cpputest,Andne/cpputest,bithium/cpputest,Andne/cpputest,PaulBussmann/cpputest,maxilai/cpputest,offa/cpputest,asgeroverby/cpputest,Mindtribe/cpputest,devMichaelJones/cpputest,Andne/cpputest,maxilai/cpputest,basvodde/cpputest,PaulBussmann/cpputest,devMichaelJones/cpputest,Andne/cpputest,offa/cpputest,devMichaelJones/cpputest,chenlianbing/cpputest,basvodde/cpputest,cpputest/cpputest,KisImre/cpputest,maxilai/cpputest,basvodde/cpputest,chenlianbing/cpputest