nrf52_bsim: Improve compile time check of HW models version

In 4940a3ca a compile time
check of the HW model version was added. This check worked
fine for cases in which the problem was that people had not
fetched a new enough version of the HW models.
But in some cases people will have fetched a new enough version
but be (unknowingly) in a past detached HEAD (or old tag).

With this change we ensure that the required tag is an actual
ancestor for the current HW models version HEAD

Also fail with an error, instead of just printing a warning.
Users can still disable this warning if they know what they are
doing.

Signed-off-by: Alberto Escolar Piedras <alpi@oticon.com>