tests: Update pip prior to installing gem5art packages

This fixes the `invalid command 'bdist_wheel'` error which may be
causing wider problems, as reported in this email thread:
https://www.mail-archive.com/gem5-dev@gem5.org/msg39790.html

The `bdist_wheel` package, a dependency of the `celery` package, was
not being installed correctly. The root cause of this
problem is not known, but solutions are presented here:
https://stackoverflow.com/questions/34819221/why-is-python-setup-py-saying-invalid-command-bdist-wheel-on-travis-ci

Upgrading pip prior to installing the gem5art packages seemed like the
simplest solution.

Change-Id: I1bd4e85871c37d0522e16a90ff6b8acc3fdd9f94
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/49044
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed