ci: make executor hash script stable
Created by: jhchabran
The executor image was built on every CI run for a while, which became apparent as we started investigating some build issues this morning. We found out that the hash.sh script was not working as intended, probably since the update to go 1.18.
Kudos to @burmudar for finding the flag that was added recently.
Test plan
tested locally, new build flag made the binary stable across HEAD and HEAD^