Lacros: Fix xvfb condition in angle For Lacros, xvfb is only used in Linux-Lacros, but not on-device config, so this CL fixes the problem. Bug: chromium:1195415 Test: built Chromium and Angle from source Change-Id: Ia9adf706716c424b14a395189755932e445b7050 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2802854 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>