The "CPU time" values printed by post_build_ninja_summary.py are not
actually measure of CPU time, they are measures of wall-clock time or
elapsed time. This just changes the labeling of the numbers - the actual
numbers printed are unchanged.

The "weighted time" number continues to be the more important number
since it is an approximation of how much the build step(s) are affecting
build time. See the comments in the script for details.

Change-Id: Ibdb4efdd327ece34492ab10337c234a826514197
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1900019
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>