tests/functional: ensure we have a GPU device for tests It's possible to build QEMU without support for the GL enabled GPU devices and we can catch that earlier with an explicit check. Reviewed-by: Thomas Huth <thuth@redhat.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20250304222439.2035603-4-alex.bennee@linaro.org>