hob: sync after image deploy

Showing "Deploy image successful" after 'dd' returns
may determine the user to disconnect the usb stick even
though the writing operations are not finished.
This patch makes sure that the entire image is deployed
on the usb stick before the user is informed about any result.

[YOCTO #5892]

Signed-off-by: Valentin Popa <valentin.popa@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
runqueue: More carefully handle the sigchld handler

We've noticed hanging processes which appear to be looping around
waitpid. Its possible multiple calls to teardown are causing problem
or in theory multiple registrations (although the code should not
allow that). Regardless, put better guards around signal handler
registration.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
runqueue: Ensure handler does not recurse

Failures on the autobuilder look like this handler is recursing. That
shouldn't be possible but it doesn't hurt to code as such.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
world-image: add extra target

* similar to world target, but collects all PACKAGES
* recipes marked with EXCLUDE_FROM_WORLD are excluded from world as well
  as world-image
* recipes marked with EXCLUDE_FROM_WORLD_IMAGE are excluded completely
  from world-image, sometimes you can build 2 recipes in same sysroot,
  but cannot install them in the same image
* PACKAGES listed in EXCLUDE_PACKAGES_FROM_WORLD_IMAGE are also
  excluded. You can remove e.g. ${PN}-dbg, but keep all other PACKAGES.

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>