More fixes to the build instructions.

This picks up various fixes noted by [email protected],
[email protected], and Twitter user @florpelier, as well as a few
more things I wanted to clean up.

[email protected], [email protected], [email protected]
BUG=

Review-Url: https://codereview.chromium.org/2543503004
Cr-Commit-Position: refs/heads/master@{#435533}
6 files changed