Port frame_analyzer and rgba_to_i420_converter targets to GN build.

Tested on Linux with the following command lines:

$ gn gen //out/Debug --args='is_debug=true target_cpu="x64" build_with_chromium=false'
$ ninja -C out/Debug frame_analyzer rgba_to_i420_converter

BUG=chromium:461019
TEST=see above
R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42999004

Cr-Commit-Position: refs/heads/master@{#8914}
4 files changed