Build with use_qt = true

This change enables QT at build time, but does not toggle the feature
flag, so there should be no user-visible changes.  libqt5_shim.so will
start getting included in the Linux packages.

R=sky

Bug: 1317782
Change-Id: Ib92d9b5d663d01aa4ace96520b3f64a4bb66df5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3877368


Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1044786}