package_manager.py: reverse archs correctly

package_manager.py: reverse archs correctly

It had reversed all the archs, which mixed multilib and common archs, e.g.:
"all any noarch x86_64 core2-64 qemux86_64 x86 i586 core2-32"
After reversed:
"core2-32 i586 x86 qemux86_64 core2-64 x86_64 noarch any all"
The core2-32 has a higher priority than core2-64 after reversed which is
incorrect. Don't mix with mulitlib when reverse can fix the problem, and let
multilib archs have a higher priority for multilib image.

Fixed:
MACHINE = "qemux86-64"
require conf/multilib.conf
MULTILIBS = "multilib:lib32"
DEFAULTTUNE_virtclass-multilib-lib32 = "core2-32"
IMAGE_INSTALL_append = " ca-certificates"

$ bitbake wrlinux-image-glibc-small
Check rootfs.manifest, no core_32 packages is installed, this is
correct, but after we build lib32-bash, it will be incorrect:
$ bitbake lib32-bash
$ bitbake wrlinux-image-glibc-small
Check rootfs.manifest, a few lib32 packages are installed, such as
lib32-bash, this is incorrect. It was because ca-certificates is
allarch, and requires /bin/sh, which is provided by both bash and
lib32-bash, and lib32-bash has a higher priority than bash, so it would
be installed.

[YOCTO #12288]

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>