Generate libaom_srcs.txt and libaom_srcs.gni via CMake.
Generate libaom_srcs.txt and libaom_srcs.gni via CMake.

BUG=aomedia:474

Change-Id: I42569ab97b5246de98310031e1d2398876283527

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom