virglrenderer: change SRC_URI to mirror

BUG=chromium:837073
TEST=emerge-eve virglrenderer

Change-Id: I5474d1cd9b2f1fdbb6b6f416cac24c44e8808584
Reviewed-on: https://chromium-review.googlesource.com/1100120
Commit-Ready: David Riley <davidriley@chromium.org>
Tested-by: David Riley <davidriley@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
1 file changed