ci: Adds /usr/local/bin to PATH at piglit-traces.sh
What does this MR do and why?
yq and ci-fairy are installed in /usr/local/bin but on script execution, that route is not included by default for all runners.
Identified on RPI4 traces jobs like this: https://gitlab.freedesktop.org/mesa/mesa/-/jobs/55242443#L672
The PATH of that job don't include /usr/local/bin. https://gitlab.freedesktop.org/mesa/mesa/-/jobs/55242443#L586