By making "v8_heap_base_headers" a "v8_header_set" instead of
a "v8_source_set".
Reported by Paul Harris on v8-users@.

Change-Id: I33263230631766e73f5d13aab497c47c98f807b1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3776339
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81845}