* Address warnings generated when compiled with gcc 4.8 and -Wall

* Don't set -Wall for external projects

* Pass CMAKE_ORIGINAL_CXX_FLAGS not CMAKE_CXX_FLAGS to external projects.

* Fix pragmas for gcc 4.8

* fix windows build
Co-authored-by: Sang Ik Lee <sang.ik.lee@intel.com>
Co-authored-by: Scott Cyphers <diyessi@users.noreply.github.com>