Bug 1698156 - Set up SWGLPP env target with null CFLAGS and CXXFLAGS. r=jrmuizel
Bug 1698156 - Set up SWGLPP env target with null CFLAGS and CXXFLAGS. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D109525

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/38a9b0040e8f2cddd1095363dc68a279efe93622

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