insane.bbclass: Make do_qa_staging check shebangs

insane.bbclass: Make do_qa_staging check shebangs

As reported in the bug report [1], there was no check for shebang
sizes on native scripts and now this is fixed.

The path scope of the qa_staging was increased from just checking
libdir to all the relevant SYSROOT_DIRS.

It is possible to skip this check through INSANE_SKIP.

[1] https://bugzilla.yoctoproject.org/show_bug.cgi?id=11053

Signed-off-by: Paulo Neves <ptsneves@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>