Librefox isn't exactly what you described, but it's close. It's a set of configs that disable a bunch of telemetry and other unauthorized mothership connectivity and settings pushing.
However, Librefox is only Firefox with some configuration changes. It is not a whole new build, and it wouldn't have protected you from this problem since the problematic addon cert checking is still there.
Note that this would have happened even if the browser never communicated back home - this problem was triggered via an unwitting time bomb of sorts, not because Mozilla actively took an action that inadvertently broke something.
https://github.com/intika/Librefox
However, Librefox is only Firefox with some configuration changes. It is not a whole new build, and it wouldn't have protected you from this problem since the problematic addon cert checking is still there.
Note that this would have happened even if the browser never communicated back home - this problem was triggered via an unwitting time bomb of sorts, not because Mozilla actively took an action that inadvertently broke something.