Compile the virtual backend with older Mesa
Summary:
BUG: 403326
FIXED-IN: 5.15.0
Test Plan: N/A
Reviewers: KWin, fvogt, davidedmundson
Reviewed By: KWin, fvogt, davidedmundson
Subscribers: kwin, fvogt
Tags: KWin
Differential Revision: https://phabricator.kde.org/D18353