Bug 1698295 - Build glsl with opt-level=2 to improve build times. r=glandium
Bug 1698295 - Build glsl with opt-level=2 to improve build times. r=glandium

This changes reduces the time spent in swgl shader translation
from 24s to 12s.

Differential Revision: https://phabricator.services.mozilla.com/D108327

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/ae9bf59a5a25f94747129da35d401a73964baff7

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender