Show Maven errors from within make-distribution.sh

This works:

./dev/make-distribution.sh \
 --pip \
 -Phadoop-2.7 -Phive -Phadoop-cloud 

 
But this doesn't:

 ./dev/make-distribution.sh \
 -Phadoop-2.7 -Phive -Phadoop-cloud \
 --pip

The latter invocation yields the following, confusing output:

 + VERSION=' -X,--debug Produce execution debug output'

 That's because Maven is accepting --pip as an option and failing, but the user doesn't get to see the error from Maven.