util,misc: Altered cpt_upgrader.py shebang to Python3
This script is necessisary for compilation yet is dependent on Python2.
On a pure Python3 system, this results in a compilation failure.
This script works fine with Python3.
Change-Id: Ib1470a76d65455e727041686788c08f385e7251a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/36715
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>