dockerd requires Xtables and nft_compat to use iptable-nft.
This is not ideal but this commit restore xtables to support dockerd

kbuild read them from environment, so only put them as makefile var is not
sufficient

Early makefile patching achieve 2 goals.
Firstly, avoid adding variables to each make call.
Secondly, it is later used by tools (e.g dkms) to build out-of-tree modules.

- Drop Xtables
- Drop MPLS
- Drop DCB
- Drop Openvswitch (because of MPLS requirement)
- Add IPv6 multicast support

- Backport fix about USB hub enumeration

- Fix tarball name
- Restore build for untagged tarballs

This make it fail to boot.

- fix perms
- strip kernel and executables
- include all headers (e.g: missing vdso/const.h)
- provides VIRTUALBOX-GUEST-MODULES WIREGUARD-MODULE
- remove documentation
- remove sources broken symlinks
- remove sources lost objects

Security patches inside !

See: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20200602&id=9f984cacf4f4d53fd8a3f44d7f13528b81c1f6a8

Because of duplicate build as CPU expensive and slow down release process.

Issue with iwlwifi.

See: https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.6-Broken-Intel-IWLWIFI