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Use the set of portable code from zlib that shouldn't have
extra dependencies (e.g. 'base').

Also allow building the tool for other targets (e.g. Linux,
OSX, etc) as that allows easier testing and profiling.

Bug: 1076580, 1087999
Change-Id: I3130ba77681ae66dc34c3539c2ed10476e754d86
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2211008
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773937}