Re-Re-land migrate md5sum tool to portable zlib utils

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.

Compilation is disabled for Windows, see crbug.com/1090428.

Bug: 1076580, 1087999
Change-Id: Id633b5aa287cd6b24c72af51a23c73d50617c68b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2227312


Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Reviewed-by: David Turner <digit@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#774555}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3d10c9b5ebd65d5b6f9562c95542a0ff2eaec8c5