Add /wd4703 for passing VS 2012 build.This equals /wd4701 in VS2015. Cc: Liming Gao <liming.gao@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Dongao Guo <dongao.guo@intel.com> Reviewed-by: Liming Gao <liming.gao@intel.com>