Add some documentation for win/cross builds, remove assert() disallowing them.

Also, in win/cross builds:
* enable clang by default
* disable NaCl by default

Bug: 495204
Change-Id: Iae3c982097970227c45450fa449f6a56d64f148f
Reviewed-on: https://chromium-review.googlesource.com/717077
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#508745}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: bf97a6d177dc974c388a5b9cd354e63582f1a367
2 files changed