Support CONFIG_CDEF in the cmake build.
Support CONFIG_CDEF in the cmake build.

BUG=https://bugs.chromium.org/p/aomedia/issues/detail?id=76

Change-Id: I3e19eb302eb2f0f5a12243bf093c8f9807d97e91

GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,luctrudeau/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom