[Build] Use -ftime-trace instead of -ftime-report.

-ftime-report prints buggy, not-too-informative tables to stdout
while -ftime-trace creates .json files for each translation unit
that can be loaded into chrome://tracing, and offers much more
useful information about e.g. how much time is spent on
creating code for or optimizing specific functions.

      files generated next to the .o files in chrome://tracing

Bug: None
Test: Turn compiler_timing on, build a target, load the .json
Change-Id: I6380c10bd94f151f20d5909676d89d0b70ee453b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1661714
Reviewed-by: Reid Kleckner <rnk@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#669714}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f919d139bb6c0905af03b115bd199f5d9f72f745
1 file changed