jack2: force host-python dependency for waf build-system

jack2 uses Waf 1.6.11. The waf configure program combines a part of
python script with a compiled blob. According to Waf documentation,
waf currently supports python interpreter from version 2.3 to 3.1.

However, Buildroot provides python-3.4. So, let's uses host python2
interpreter for building jack2.

This patch also cleanup whitespace, replacing wrongly used spaces with
tabs.

Fixed:
  http://autobuild.buildroot.net/results/913/913bb1836076be9f201bf6641c7614708d6916bc/



Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>