retiring arm oabi support for new things

[matthew green <mrg%eterna.com.au@localhost>]

hi folks.


netbsd 9 will ship without any targets with oabi as the
default, and most of the existing ports were already
switched to eabi (epoc32 and acorn32 only.)

as part of this, i'm going to stop providing the ability
to build any arm with oabi -- turn off the MKCOMPAT for
all arm ports, so the oabi libraries are not provided
anymore, turn off the oabi ld.elf.so, etc.

i will not be removing the ability to execute these
binaries, but their supplimental files (ld.so, shlibs)
will need to be supplied from a prior release if the
old binaries are still required.  there should not be
any issue here, as the kernel support is fairly simple
and doesn't need to change.

i'm pretty sure this won't affect anyone.  if you have
upgraded to an eabi release, with oabi shlibs provided,
you were already happy.  if you're running very old
netbsd, then upgrading to netbsd-9 and then beyond will
be the solution to keep your shlibs at highest level.

this should reduce the build time of the whole cluster.
there are about 15 arm ports in total, and turning off
all their shlib builds will probably save a noticeable
fraction of the total.

any comments?


.mrg.