rootfs.py: fix run-postinsts removal on multilib images

ROOTFS_BOOTSTRAP_INSTALL in image.bbclass unconditionally stages
run-postinsts into every image. When no delayed postinsts remain,
_uninstall_unneeded() is supposed to remove it again, but the removal
call used the bare "run-postinsts" package name without applying
MLPREFIX.

On a multilib image (e.g. lib32-core-image-minimal), the package that
is actually installed is lib32-run-postinsts, so the unprefixed
removal silently matches nothing and run-postinsts leaks into the
final image manifest, along with its now-pointless init script /
systemd unit.

Expand MLPREFIX before removing the package, matching the pattern
already used elsewhere in oe-core (e.g. oe/package.py) for
package-name lookups that need to work across multilib variants.

(From OE-Core rev: 2522a1ad4fb66af0a9ca146ca7a88aece8f471da)

Signed-off-by: Kyungjik Min <dp.min@lge.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit dfa5673907bdc5211671ecdfce8ab1fb332eae48)
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/lib/oe/rootfs.py

@@ -266,7 +266,8 @@ class Rootfs(object, metaclass=ABCMeta):
         delayed_postinsts = self._get_delayed_postinsts()
         if delayed_postinsts is None:
             if os.path.exists(self.d.expand("${IMAGE_ROOTFS}${sysconfdir}/init.d/run-postinsts")) or os.path.exists(self.d.expand("${IMAGE_ROOTFS}${systemd_system_unitdir}/run-postinsts.service")):
-                self.pm.remove(["run-postinsts"])
+                mlprefix = self.d.getVar('MLPREFIX') or ""
+                self.pm.remove([mlprefix + "run-postinsts"])
 
         image_rorfs = bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs",
                                         True, False, self.d) and \