Update buildroot to 2024.02.3 LTS release

[brandond]

• Update to release 2024.02.3.
• Update build env to SLE 15.6.
• Drop local package for slirp4netns, it has been upstreamed.
• Add xargs from findutils; it has always been built but not included
• Drop xargs applet from busybox, it has always been included but not
  linked.
• Drop ppc64 and s390x since we are no longer producing K3s for these
  platforms. We'll leave riscv64 since it may be coming at some point in
  the future.

[dereknola]

Any particular reason we are moving off bci-base? A 15.6 version of it does exist https://registry.suse.com/repositories/bci-bci-base-15sp6?tag=15.6.

[brandond]

They're the same image.

brandond@dev01:~$ skopeo inspect --raw docker://registry.suse.com/suse/sle15:15.6 | sha256sum
0b0aa0d0fd58bc617120898436ff0661fac936158f52a444afef6a25a07fc4d9  -
brandond@dev01:~$ skopeo inspect --raw docker://registry.suse.com/bci/bci-base:15.6 | sha256sum
0b0aa0d0fd58bc617120898436ff0661fac936158f52a444afef6a25a07fc4d9  -

This just addresses the inconsistency between the fossa and build steps.

[brandond]

Just for the record:

brandond@dev01:~/go/src/github.com/k3s-io/k3s-root$ diff -u old-root.txt new-root.txt
--- old-root.txt	2024-07-09 17:00:23.668756396 +0000
+++ new-root.txt	2024-07-09 17:00:32.720755618 +0000
@@ -22,6 +22,7 @@
 ./bin/aux/ebtables-nft-save -> xtables-nft-multi
 ./bin/aux/ebtables-restore -> xtables-nft-multi
 ./bin/aux/ebtables-save -> xtables-nft-multi
+./bin/aux/ebtables-translate -> xtables-nft-multi
 ./bin/aux/ebtablesd
 ./bin/aux/ebtablesu
 ./bin/aux/ip6tables -> iptables-detect.sh
@@ -339,6 +340,7 @@
 ./bin/which -> busybox
 ./bin/who -> coreutils
 ./bin/whoami -> coreutils
+./bin/xargs
 ./bin/xxd -> busybox
 ./bin/xz -> busybox
 ./bin/xzcat -> busybox
 
brandond@dev01:~/go/src/github.com/k3s-io/k3s-root$ tar -tvf dist/k3s-root-amd64.tar | grep xargs
-rwxr-xr-x root/root     96000 2024-07-09 08:39 ./bin/xargs
 
brandond@dev01:~/go/src/github.com/k3s-io/k3s-root$ ls -la dist/*root-amd64*
-rw-r--r-- 1 brandond brandond 8130560 Jul  9 08:39 dist/k3s-root-amd64.tar
-rw-rw-r-- 1 brandond brandond 8099840 Jul  9 17:02 dist/old-k3s-root-amd64.tar

Without compression this release is ~30kb larger; xargs is 93kb but some of that is made up for by removal of xargs from busybox, and other misc reductions in binary size.