Correct zlib build logic for Windows on Arm

Fixes a failing GN assertion for Windows on Arm as it uses a separate
path to check CRC32 extension support, so no OS-specific defines are
needed.

Bug: 810125
Change-Id: I172b4ecd66d94d195f1ccac4c6108ea2a40972a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1567678


Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Commit-Queue: Richard Townsend <richard.townsend@arm.com>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#651040}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 38bf6e359de031ec11566e446d6f7bbcd4dfc9d6