How to set the julia optimization level for each run on Github Actions?

I have this script, where I have the following matrix:

        julia-version: ['1', '1.6', '~1.9.0-0']

and the following command to launch julia

        shell: julia --color=yes --project=downstream {0}

I want to specify an optimization level -O0 for the runs on julia versions v1 and v1.9, but not for v1.6. I am not that familiar with GitHub actions, and I was wondering if someone could suggest a way to achieve this?