Adds additional checks and PYTHON_DEFAULT_INTERP var that is used to
find the correct python binary as well as checks to see if the
_python2-mraa or _python3-mraa targets have been built by checking
mraa.py. This does assume that this is all that is needed as checking
for TARGET() is not enough as the target is always 'valid'. We prefer
python2 and will only run the java tests if we can find python2
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
1d37d3b162