linux-imx

docs: Completely fix the remote build tree case

My previous fix miserably failed to catch all of the invocations of
"./scripts/sphinx-pre-install", so we got build errors.  Try again with
more caffeine.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>