v2:
  - Update the README.md with further documentation.

v3:
  - Exit with "1" when the inner result is negative, marking a CRASH,
    and with "2" when the inner result is positive, marking a FAIL.

v4:
  - Use newly added compare result enumeration.

Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Part-of: <mesa/piglit!353>