runner/meson.build: fix minimal build

Minimal pipeline s now failing:
	https://gitlab.freedesktop.org/gfx-ci/igt-ci-tags/-/jobs/38824636



This doesn't seem to be related to the patches at the series from
where the issue was reported, but addressing it is simple enough:
just remove the error and change the logic to properly validate
the possible options.

Acked-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>