Resolve path to right licheck

In the unix commercial packages, licheck so far has been a shell
script that redirected to the 'right' licheck. To simplify things
we now resolve the right executable path in configure itself.

Change-Id: I1183d000a11bf42729f3e0405a0bc1d4b618933c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>