Improve the architecture-detection mechanism

Improve the architecture-detection mechanism

For the Unix part, this now obeys the -v option, printing the full
command-line it used to compile, allowing testers to identify why
something went wrong.

Unfortunately, it requires a full compilation cycle, instead of just
preprocessing. Just one more among the many on Unix, but maybe a
noticeable slow-down on Windows.

Change-Id: I654b70d99887e04c96731a5b91be9ad555e4d8fe
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>