armv6: Remove support for building armv6

[andrew]

Summary

With it planned that armv7 will be the only 32-bit kernel when 15.0 is
released remove support for armv6.

Remove the top level build infrastructure. It was already removed from
universe, this just stops it from being built directly.

Sponsored by: Arm Ltd

[mmel]

Makefile

534–535

Do we need both TOOLCHAINS_arm and TOOLCHAIN_armv7? It looks like it's not consistent with the other arches.

[imp]

Looks good so far, with the one comnent addressed

[emaste]

LGTM; the duplication @mmel points out is curious, but it looks like it's consistent with powerpc

[andrew]

Rebase + remove TOOLCHAIN_armv7

[emaste]

Also make sure there's a Relnotes: Yes

[andrew]

We should disable armv6-main in CI before committing, otherwise it will likely spam on each commit after this (cc @lwhsu)

[lwhsu]

In D45634#1041813, @andrew wrote:

We should disable armv6-main in CI before committing, otherwise it will likely spam on each commit after this (cc @lwhsu)

Sorry for the delay, the the main-armv6 job is disabled and the related configurations are removed.