When buid with "is_component_build=true" will failed.
  Add lib atomic into lib in v8_libplatform.
  Move func body into cc file

Bug: v8:11975
Change-Id: Ifb844a82360310aba444504f7012fa0c543a49e9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3046980
Auto-Submit: Yahan Lu <yahan@iscas.ac.cn>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Brice Dobry <brice.dobry@futurewei.com>
Reviewed-by: Ji Qiu <qiuji@iscas.ac.cn>
Commit-Queue: Brice Dobry <brice.dobry@futurewei.com>
Cr-Commit-Position: refs/heads/master@{#75919}