tools/debug_helper:run_mkgrokdump used to only depend on mkgrokdump.
However, the snapshot can change without affecting the mkgrokdump
binary itself. So, if the mkgrokdump binary doesn't change, then
run_mkgrokdump doesn't run, even if the snapshot changed.

This could cause mysterious test failures in incremental builds, in
particular for tests testing the contents of heap-constants-gen.cc.

Now, we make run_mkgrokdump depend on run_mksnapshot_default
directly, so that snapshot updates force an mkgrokdump run.

Change-Id: Ia3871e1b4fa15ec2dbc0bc5463afdb427cb39c61
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2400987
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69776}