Enable parallelization on dsymutil

Also adjusted the memory size per link accordingly. Previous CL did not
account for ThinLTO builds.

Bug: 532150826
Change-Id: I26993a1dc99b8c2f9ebc28530d41210b5085d4f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8183146
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Yue She <yueshe@google.com>
Cr-Commit-Position: refs/heads/main@{#1674119}
NOKEYCHECK=True
GitOrigin-RevId: 255ebdc12ba0420cf835739a4f18dfd7a63e580c