When .got2 is empty, the orphan .data.rel.ro output section follows
.dynamic and inherits both its :kernel and :dynamic program-header
assignments. This makes PT_DYNAMIC cover .data.rel.ro as well as the
actual dynamic table. On powerpc64le, its resulting size may not even
be a multiple of Elf64_Dyn.
Describe .data.rel.ro explicitly and assign it only to :kernel,
terminating :dynamic inheritance on powerpc, powerpc64, and powerpc64le.
MFC after: 2 weeks
MFC to: stable/14, stable/15
Sponsored by: FreeBSD Foundation, Reliable Computer Systems Lab