[PATCH 0/9] Enable arm64 host support in Gitlab

[Tom Rini]

Hey all,

First, thanks to Simon Glass and also Linaro, we now have access to a
few fast arm64 host machines in our Gitlab instance, to use as CI
runners. This series finishes the work that I pushed earlier and Simon
had started that enables arm64 hosts to be used for most things now.

The first notable change, especially if you use this on your own Gitlab
instance is that "DEFAULT_TAG" is now unused and we instead have:
- DEFAULT_ALL_TAG:
- DEFAULT_ARM64_TAG:
- DEFAULT_AMD64_TAG:
- DEFAULT_FAST_AMD64_TAG:

This lets us say that some jobs can be run on all runners, because they
are small enough that anything we'd connect to CI is fast enough and it
also does not depend on the underlying host architecture. Next we have
tags for any arm64 host, or any amd64 host. Finally, we have a tag for
fast amd64 hosts. What these last three are for is that we have a few
jobs that need to run on amd64 hosts and so we have to restrict them
there, but we also have now reworked the world build jobs to build
(almost) everything in a single job and on the fast amd64 machines this
is still as quick as the old way was, in practice.

To reach this point, we say that the Xtensa jobs can only run on amd64
hosts. Our targets only work with the binary-only toolchain and so this
is a reasonable limit and we exclude them from the world build jobs. We
also need to deal with ensuring the right toolchain is used regardless
what the host architecture is and that we don't use the host toolchain
by accident. Finally, because some of these changes needed to be worked
out in the linter, fix some of the general warnings that notes as well.

-- 
Tom