Update the GN build with the cpu_arch -> current_cpu rename. R=andrew@webrtc.org, rtoy@google.com, rtoy@chromium.org BUG=crbug.com/344767 Review URL: https://webrtc-codereview.appspot.com/39249005 git-svn-id: http://webrtc.googlecode.com/svn/deps/third_party/openmax@8451 4adac7df-926f-26a2-2b94-8c16560cd09d