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

[Hans-Peter Nilsson]

> From: Alan Modra <amodra@gmail.com>
> Date: Tue, 12 Aug 2014 15:14:43 +0200

> This is what I have here, so far.  I'm going to leave committing this
> for a little while to let others comment.
> 
>     configury changes to make ld plugin support controlled by --enable-plugins
>     
>     This also makes --enable-plugins default to on for hosts that can
>     support plugins, so we have consistent lto toolchain support.  The
>     ACX_LARGEFILE moves aren't strictly necessary, but are harmless and
>     will be necessary if plugin support is extended to more hosts via
>     libtool's dlopen support.  I started down that path then decided it
>     was more work than I was interested in doing.  (ACX_LARGEFILE invokes
>     AC_PLUGINS.)
>     
>     	* config/plugins.m4: Test for dlfcn.h or windows.h here to set
>     	default for --enable-plugins.  Report error if someone tries to
>     	enable plugins on a host we don't support.
>     bfd/
>     	* configure.ac: Delete redundant plugin related checks.
>     	* configure: Regenerate.

Needed for (gdb and) sim too?  It seems to have broken all
simulators, or at least those for arm-eabi, cris-elf, d10v-elf,
frv-elf, h8300-elf, iq2000-elf, m32c-elf, m32r-elf, m68hc11-elf,
mcore-elf, mips-elf, mn10300-elf, powerpc-eabisim, sh-elf,
v850-elf like so:

gcc -DHAVE_CONFIG_H     -DPROFILE=1 -DWITH_PROFILE=-1          -DDEFAULT_INLINE=0           -DMODET -DNEED_UI_LOOP_HOOK -DSIM_TARGET_SWITCHES   -I. -I/tmp/hpautotest-sim/src/sim/arm -I../common -I/tmp/hpautotest-sim/src/sim/arm/../common -I../../include -I/tmp/hpautotest-sim/src/sim/arm/../../include -I../../bfd -I/tmp/hpautotest-sim/src/sim/arm/../../bfd -I../../opcodes -I/tmp/hpautotest-sim/src/sim/arm/../../opcodes  -g -O2 -static-libstdc++ -static-libgcc  -o run \
	  run.o libsim.a ../../bfd/libbfd.a ../../opcodes/libopcodes.a  ../../libiberty/libiberty.a -lz -lnsl   
../../bfd/libbfd.a(plugin.o): In function `try_load_plugin':
/tmp/hpautotest-sim/src/bfd/plugin.c:168: undefined reference to `dlopen'
/tmp/hpautotest-sim/src/bfd/plugin.c:175: undefined reference to `dlsym'
/tmp/hpautotest-sim/src/bfd/plugin.c:171: undefined reference to `dlerror'
collect2: error: ld returned 1 exit status
make[3]: Leaving directory `/tmp/hpautotest-sim/arm-eabi/sim/arm'

brgds, H-P