tools/building: remove the use of startupinfo
tools/building: remove the use of startupinfo

The startupinfo does not have any visible effects on the building
process and some old Python version does not have it at all. So remove
it for the seek of simple.

Tested `scons -j4` in a dual core virtual machine.

zhaojuntao/rt-thread,igou/rt-thread,FlyLu/rt-thread,weety/rt-thread,wolfgangz2013/rt-thread,wolfgangz2013/rt-thread,RT-Thread/rt-thread,armink/rt-thread,AubrCool/rt-thread,zhaojuntao/rt-thread,ArdaFu/rt-thread,nongxiaoming/rt-thread,geniusgogo/rt-thread,wolfgangz2013/rt-thread,RT-Thread/rt-thread,FlyLu/rt-thread,yongli3/rt-thread,weiyuliang/rt-thread,igou/rt-thread,weiyuliang/rt-thread,ArdaFu/rt-thread,FlyLu/rt-thread,RT-Thread/rt-thread,geniusgogo/rt-thread,weiyuliang/rt-thread,igou/rt-thread,armink/rt-thread,yongli3/rt-thread,RT-Thread/rt-thread,weety/rt-thread,FlyLu/rt-thread,wolfgangz2013/rt-thread,armink/rt-thread,zhaojuntao/rt-thread,weety/rt-thread,yongli3/rt-thread,FlyLu/rt-thread,RT-Thread/rt-thread,hezlog/rt-thread,igou/rt-thread,ArdaFu/rt-thread,hezlog/rt-thread,geniusgogo/rt-thread,FlyLu/rt-thread,armink/rt-thread,geniusgogo/rt-thread,gbcwbz/rt-thread,igou/rt-thread,nongxiaoming/rt-thread,gbcwbz/rt-thread,ArdaFu/rt-thread,geniusgogo/rt-thread,AubrCool/rt-thread,hezlog/rt-thread,gbcwbz/rt-thread,nongxiaoming/rt-thread,wolfgangz2013/rt-thread,zhaojuntao/rt-thread,weiyuliang/rt-thread,weety/rt-thread,weety/rt-thread,FlyLu/rt-thread,weety/rt-thread,igou/rt-thread,AubrCool/rt-thread,AubrCool/rt-thread,weiyuliang/rt-thread,weiyuliang/rt-thread,zhaojuntao/rt-thread,yongli3/rt-thread,wolfgangz2013/rt-thread,hezlog/rt-thread,AubrCool/rt-thread,AubrCool/rt-thread,nongxiaoming/rt-thread,nongxiaoming/rt-thread,yongli3/rt-thread,gbcwbz/rt-thread,RT-Thread/rt-thread,nongxiaoming/rt-thread,RT-Thread/rt-thread,AubrCool/rt-thread,geniusgogo/rt-thread,weety/rt-thread,armink/rt-thread,ArdaFu/rt-thread,gbcwbz/rt-thread,wolfgangz2013/rt-thread,zhaojuntao/rt-thread,armink/rt-thread,weiyuliang/rt-thread,ArdaFu/rt-thread,nongxiaoming/rt-thread,yongli3/rt-thread,yongli3/rt-thread,hezlog/rt-thread,geniusgogo/rt-thread,ArdaFu/rt-thread,zhaojuntao/rt-thread,hezlog/rt-thread,igou/rt-thread,gbcwbz/rt-thread,gbcwbz/rt-thread,armink/rt-thread,hezlog/rt-thread