Re-land "Enable dSYMS in runtime_deps on official mac builds properly."

This reverts commit 5c5db6461a98651d65af70f1abaa6d6283a93b65 and
re-lands f090d8b6a02e69611e0d180f6e39d584d1f8aad1
with a fix to correct the .dSYM path for plugins; this fix won't
work if the plugin doesn't end in .so, but currently, neither
will the rest of the mac_plugin_bundle template.

R=bpastene@chromium.org
BUG=961548

Change-Id: Iaf520829cfcb495985d1dfdb3788f58a41936597
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1674406
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#671789}