I noticed in a recent build that C++ files from cctest didn't start
compiling until after several slow non-parallel tasks such as running
mksnapshot and linking v8_for_testing. I don't see any reason that
cctest sources should wait for those tasks, so in this change I propose
adjusting the build dependencies for more parallelism.

Change-Id: I2472117c8555ac397fa1232954c8b699d6429d38
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3690170Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#80976}