GN/Win: quieter builds

GN/Win: quieter builds

It's hard to read the logs as they are now.  This simplifies down the descriptions, and stifles a warning about linking object files with no symbols into a static library.

CQ_INCLUDE_TRYBOTS=master.client.skia.compile:Build-Win-MSVC-x86-Debug-Exceptions-Trybot,Build-Win-MSVC-x86_64-Debug-GN-Trybot,Build-Win-MSVC-x86_64-Release-GN-Trybot
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3322

Change-Id: I52beb3b8405ebb2c370cad432669834b64baa840
Reviewed-on: https://skia-review.googlesource.com/3322
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>