Add time_exploded_posix to gn bootstrap.

TBR=brettw@chromium.org

Change-Id: Ib394ea8b5a2ff5536ba66ac7fcc2cbfac7e4d53e
Reviewed-on: https://chromium-review.googlesource.com/840457
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#525763}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c2c9d071b16d5ceea770519060d90e97cb8b5274