Mig-generated files contain mig identifiers, which include timestamp and mig build info.
To improve build determinism and goma cachehits we can replace these lines with something stable.
Bug: crashpad:390
Change-Id: Iedb2f6e64428612899587c2ac4d488baf439961f
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3394052
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Mark Mentovai <mark@chromium.org>