package_manager.py: rework postinst_intercept failures

Previously a warning was printed regardless of context and nature
of the failure, and because it was only a warning, it was mostly ignored.

Now, the following is considered when a failure happens:
1) whether we are installing packages into a target image, or populating
a SDK with host or target packages.
2) whether the failure was due to qemu not supporting the target machine.

Accordingly, warnings, notes, and failures are printed, and postponing
to first boot happens if possible.

(From OE-Core rev: a335e78672b1e1ae3ea6427f6a805218e513bb52)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemuwrapper-cross_1.0.bb

@@ -20,6 +20,11 @@ do_install () {
 #!/bin/sh
 set -x
 
+if [ ${@bb.utils.contains('MACHINE_FEATURES', 'qemu-usermode', 'True', 'False', d)} = False ]; then
+        echo "qemuwrapper: qemu usermode is not supported"
+fi
+
+
 $qemu_binary $qemu_options "\$@"
 EOF