Refactor unified modules to generate targets independent of the platform.

Bug: 500845363
Link: https://chromium-review.googlesource.com/id/I63dd7268a9130faafa5023c22e1fc7db6a6a6964
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7782566
Commit-Queue: Matt Stark <msta@google.com>
Reviewed-by: Junji Watanabe <jwata@google.com>
Cr-Commit-Position: refs/heads/main@{#1618638}
NOKEYCHECK=True
GitOrigin-RevId: 8e986ff8c186db3e94bef713dc0ac5249f0b2f9d