clang docs: Tweak docs on using a local clang on Windows

Bug: none
Change-Id: I90e76f3c0c441fbbb32449cb7a85c8da774e643a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1849122
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704251}
1 file changed