OpenVDB Compile Size

[clalancette]

@Timple

If there isn’t a maximum duration for the jobs, we might be able to enforce something like MAKEFLAGS=-j1 for the buildfarm.

There is a maximum duration (2 hours), but I don’t think that matters anyway; the buildfarm by default already uses MAKEFLAGS=-j1, as far as I understand (@nuclearsandwich can confirm).