This change introduces the ability in twister to select which
emulation/simulation tool to use on the command line.
If none is specified, it will select the first in the list.
Signed-off-by: Wilfried Chauveau <wilfried.chauveau@arm.com>
Added a unit test for the platform.py module.
It covers 99% of the code. The 1% is unreachable.
Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>