Mention +x thing in clang-format upload readme.
Mention +x thing in clang-format upload readme.

BUG=427454
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/706933004

SuYiling/chrome_buildtools,SuYiling/chrome_buildtools,SuYiling/chrome_buildtools,azunite/chrome_buildtools,azunite/chrome_buildtools,azunite/chrome_buildtools