opkg-utils: Fix update-alternatives link relocation

Recently Debian-style support for link relocation was added to
'update-alternatives' script, but it fails under circumstances where
host rootfs root directory differs from target rootfs root directory
and two alternative packages provide a symbolic link with source
located in different directories.

An example of the case is busybox provided /bin/rev (symlinking to
/bin/busybox.nosuid) and util-linux provided /usr/bin/rev (symlinking
to /usr/bin/rev.util-linux) in which case following failure occurs
during image recipe's do_rootfs() task:

  ERROR: core-image-minimal-1.0-r0 do_rootfs: Postinstall scriptlets of ['util-linux'] have failed. If the intention is to defer them to first boot,
  then please place them into pkg_postinst_ontarget_${PN} ().
  Deferring to first boot via 'exit 1' is no longer supported.
  Details of the failure are in .../tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_rootfs.
  ERROR: core-image-minimal-1.0-r0 do_rootfs: Function failed: do_rootfs

Looking in log.do_rootfs file, following relevant lines can be observed:

  update-alternatives: renaming rev link from /bin/rev to /usr/bin/rev
  mv: cannot stat '/bin/rev': No such file or directory

Mitigate issue by applying patch which adds target root filesystem root
directory path prefix to failing 'mv' calls relevant variable references

(From OE-Core rev: f0912e23629758fe4303284e7db8f4089bb7b4cb)

(From OE-Core rev: 58f062843008c42d28f14c42fb5f991aef73728e)

Signed-off-by: Niko Mauno <niko.mauno@iki.fi>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/opkg-utils/opkg-utils/0001-update-alternatives-Fix-link-relocation-support.patch

@@ -0,0 +1,40 @@
+From 18562ccae6996431d37767653b061d4e9e1b9424 Mon Sep 17 00:00:00 2001
+From: Niko Mauno <niko.mauno@iki.fi>
+Date: Sun, 11 Nov 2018 15:50:22 +0200
+Subject: [opkg-utils PATCH] update-alternatives: Fix link relocation support
+
+Commit fcb26339000021eb9bb711aa264247aebcfdd4ae which added Debian-style
+support for link relocation tries to relocate symbolic link on host OS,
+resulting in following-like error when two alternative packages have
+symbolic link source located in different directories (/bin/rev ->
+/bin/busybox.nosuid and /usr/bin/rev -> /usr/bin/rev.util-linux):
+
+  update-alternatives: renaming rev link from /bin/rev to /usr/bin/rev
+  mv: cannot stat '/bin/rev': No such file or directory
+
+Fix the issue by prefixing 'olink' and 'link' variable references with
+path to targeted root filesystem's root directory.
+
+Upstream-Status: Submitted [opkg-utils]
+
+Signed-off-by: Niko Mauno <niko.mauno@iki.fi>
+---
+ update-alternatives | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/update-alternatives b/update-alternatives
+index 89a440b..d4fa7eb 100644
+--- a/update-alternatives
++++ b/update-alternatives
+@@ -58,7 +58,7 @@ register_alt() {
+ 			local link_str=`echo $link | protect_slashes`
+ 			sed -e "1s/.*/$link_str/" $ad/$name > $ad/$name.new
+ 			mv $ad/$name.new $ad/$name
+-			mv $olink $link
++			mv $OPKG_OFFLINE_ROOT$olink $OPKG_OFFLINE_ROOT$link
+ 		fi
+ 	else
+ 		echo "$link" > "$ad/$name"
+-- 
+2.19.1
+

meta/recipes-devtools/opkg-utils/opkg-utils_0.3.6.bb

@@ -13,6 +13,7 @@ SRC_URI = "http://git.yoctoproject.org/cgit/cgit.cgi/${BPN}/snapshot/${BPN}-${PV
            file://0002-opkg-build-Use-local-time-for-build_date-since-opkg-.patch \
            file://threaded-xz.patch \
            file://pigz.patch \
+           file://0001-update-alternatives-Fix-link-relocation-support.patch \
 "
 SRC_URI_append_class-native = " file://tar_ignore_error.patch"
 UPSTREAM_CHECK_URI = "http://git.yoctoproject.org/cgit/cgit.cgi/opkg-utils/refs/"