Fix ninja build
Fix ninja build

CPPFLAGS, which include the NACL_SDK_ROOT/include directory
were not previously be passed to the ninja build.

TBR=bradnelson

Review URL: https://codereview.chromium.org/801533003

Schibum/naclports,Schibum/naclports,yeyus/naclports,yeyus/naclports,yeyus/naclports,Schibum/naclports,Schibum/naclports,yeyus/naclports,yeyus/naclports,Schibum/naclports,Schibum/naclports,yeyus/naclports