Use /usr/bin/env python for the shebang in tools/generate-operator-out.py

This allows you to use a python binary that is in a non standard place.
Particularly useful if you're using a python2 virtual environment and
your system python is python3.

Change-Id: Ifb32feadffabf7a6263a8688a20fb005fa43b9da
Merge branch 'kk4.4' of https://github.com/SlimRoms/android_art into kk4.4
Fix NewLocalRef, NewGlobalRef to handle cleared weak globals.

We were not checking for null after decoding the reference, this
meant that we incorrectly created null weak global references instead
of returning null.

Issue: 63929
Change-Id: I9159682e6edad8f415ef8144fc13b9aedd2cceb4