SkQP: Cloud Scripts

  - tools/skqp/generate_gn_args.sh - single script to generate
    configuration used to build SkQP.
  - tools/skqp/make_model.sh - script to execute make_gmkb.go and put
    the results in the correct place.
  - tools/skqp/{up,down}load_directory_contents.sh - scripts to move
    large assets into the cloud and retrieve them.
  - tools/skqp/gm_runner.cpp - treat missing text files as empty.
  - tools/skqp/make_apk.sh - make use of generate_gn_args.sh.
  - tools/skqp/make_{model,known_tests}.sh - better error handling,
    and also stop calling `git add`.

Change-Id: Ib1803b4d68e63945f2c47f8eb6cb96375d24e3be
Reviewed-on: https://skia-review.googlesource.com/98842
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
13 files changed