fix gn builds on aix

Introduces `is_aix` variable and suppress non-virtual-dtor warning.

Change-Id: Iab0ceee2309d96b1efcb09fadc710362159da752
Reviewed-on: https://chromium-review.googlesource.com/1103535
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574143}
3 files changed