Configure Zucchini to use the system allocator

Zucchini uses a lot of memory, in particular when creating diffs for
very large files.

Partition alloc, by default, blocks allocations greater than 2GiB in
size but the system allocator is able to handle these larger
allocations.

A 'copy' build step is added to make sure the binary (zucchini.exe or
zucchini64.exe) and the symbols end up in the same directory as before
so no scripts will need updating.

BUG=498512075

Change-Id: I653a0723cc469f56768a55e55fe4829d37404f86
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7728046
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Will Harris <wfh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1612340}