Add debug symbols to all generated .isolate.
Add debug symbols to all generated .isolate.

This will increase the amount of data being uploaded by a ~2x factor or so.
Debug symbols are usually larger than the executable itself on pretty much all
toolsets but generally have the advantage of being highly compressible. The
increase of data not a problem anymore with isolate-go. There will be a small
increase of latency but it should be bearable, especially by the gain of
enabling stack traces to work for isolated tests on Swarming.

R=jam@chromium.org
BUG=98637
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1245703002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#349231}

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