add -j to make_options in scripts

In the scripts/pyivastest family of scripts, some of the scripts (especially scripts/IvasBuildAndRunChecks.py) also build the codec binaries for you using make. They, however, do not make use of the parallel building (-j flag) capabilities of make. This MR adds this to the scripts per default. On my machine, it saves around 1min 30s of building time, which is insignificant for most sanitizer jobs, but does come in handy when using the script to reproduce something locally.