Yes, I really don't know.  CPU isn't so much the concern, anyway.  Let those builder churn away for long periods of time.  Bwahahahaha!

But memory, now, that's an issue.  All I know for sure is that the x86_64 and i686 builds succeeded, so those boxes had "enough" memory; the ARM build failed, so that box did not have "enough" memory.  Since memory is exhausted while compiling the test, not while running the test, the required amount of memory isn't necessarily fixed.  It may depend on architecture, version of the compiler, and possibly other factors that I don't know about.  I really don't know what "enough" is, therefore ...