insane.bbclass: use multiprocessing for collecting 'objdump -p' output

insane.bbclass: use multiprocessing for collecting 'objdump -p' output

This was prompted by ltp's unreasonably long package_qa times; it has
a massive amount of executables and insane runs objdump for all of
them, serially.

This reduces the time from 4 minutes to 1m20s on my machine.

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>