b) Extend the approach taken by the x32 ABI, and use the 64-bit
native structure layout for rusage on all architectures with new
system calls that is otherwise compatible. A possible problem here
is that we end up with incompatible definitions of rusage between
/usr/include/linux/resource.h and /usr/include/bits/resource.h
c) Change the definition of struct rusage to be independent of
time_t. This is the easiest change, as it does not involve new system
call entry points, but it has the risk of introducing compile-time
incompatibilities with user space sources that rely on the type
of ru_utime and ru_stime.
I'm picking approch c) for its simplicity, but I'd like to hear from
others whether they would prefer a different approach.