Skip ld/lto tests if plugins is disabled for binutils?

[Hans-Peter Nilsson]

> From: Hans-Peter Nilsson <hp@axis.com>
> Date: Fri, 15 Aug 2014 17:17:13 +0200

> I'd rather fix up the broken pieces of "plugin support"
> (just there to pacify bfd's need) that actually *are* in sim
> already and look like they *should* pull in -ldl.  See
> sim/common/{configure.ac,Make-common.in}; I'm looking into it.

Looks like all that's actually needed is to regenerate
sim/*/configure, for example by means of "make autoconf-common"
in sim. Will do later; no keys here.

brgds, H-P