build: i386/pc686/appstart.o is created more than once

[Sebastian Huber]

In this build specification item

​https://git.rtems.org/rtems/tree/spec/build/bsps/i386/pc386/objsmpstart.yml

is an error:

* Node /home/EB/sebastian_h/git-rtems-6/build/i386/pc686/appstart.o is created more than once. The task generators are:
  1. bld(target=['appstart.o'], idx=14, tg_idx_count=14, meths=['check_err_features', 'check_err_order', 'process_rule', 'process_source'], rule='${OBJCOPY} -I binary -O elf32-i386 -B i386 ${SRC} ${TGT}', _name='appstart.o', source=[], path=/home/EB/sebastian_h/git-rtems-6, posted=True, features=[]) in /home/EB/sebastian_h/git-rtems-6
  2. bld(target='/bsps/i386/pc386/objsmpstart', idx=15, tmp_use_objects=False, tg_idx_count=15, meths=['check_err_features', 'check_err_order', 'process_rule', 'process_source'], tmp_use_stlib=True, _name='/bsps/i386/pc386/objsmpstart', source=[/home/EB/sebastian_h/git-rtems-6/build/i386/pc686/appstart.o], tmp_use_var='', path=/home/EB/sebastian_h/git-rtems-6, posted=True, typ='objects', features=[]) in /home/EB/sebastian_h/git-rtems-6
If you think that this is an error, set no_errcheck_out on the task instance

All what we have to do is to add a specially produced appstart.o to librtemsbsp.a.

[Sebastian Huber <sebastian.huber@…>]

In 9979042/rtems:

build: Fix multiple defintion error for i386/pc386

Make the objcopy an bld.objects() task generator.

Close #4079.