Bug 1700339 - Use /clang:-undef to undefine predefined macros when clang-cl is used. r=lsalzman
Bug 1700339 - Use /clang:-undef to undefine predefined macros when clang-cl is used. r=lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D109500

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/656fec3d16a848cd1333c199649bf3fa8b7f5d92

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