ld: tests: add -msim when testing bfin targets

ld: tests: add -msim when testing bfin targets

The Blackfin ELF compiler requires the user to explicitly select a CPU
target else it will fail:
bfin-elf-gcc: error: no processor type specified for linking

Select the sim target for these tests since we should (hopefully) have
access to the simulator.  At least, it's more likely than having access
to a real development board.

This makes the pass/fail numbers increase by a lot:
-# of expected passes        398
-# of unexpected failures    6
+# of expected passes        587
+# of unexpected failures    109

It looks like the vast majority of new failures are due to our omission
of COPY relocations:
  /* Bfin does not currently have a COPY reloc.  */
  if ((h->root.u.def.section->flags & SEC_ALLOC) != 0)
    {
      _bfd_error_handler (_("the bfin target does not currently support the generation of copy relocations"));
      return FALSE;
    }

There doesn't seem to be a way to easily disable tests that cause copy
relocations though, lets just take the hit for now.

	* testsuite/config/default.exp [bfin*-elf*] (gcc_B_opt): Append -msim.