[OE-core] buildtools-extended-tarball wrapping builds

[Richard Purdie]

Hi,

I just wanted to mention that we now have the ability to wrap builds on
specific workers with specific buildtools tarballs.

Currently this functionality is in master, we do have the option of
porting the helper code to other stable branches.

We have had multiple issues, with the infrastucture internal url/cert
handling, git/cert environment issues, an issue with eSDK testing (next
has a fix in testing), the crypt fix already submitted (meaning M2's
tarball doesn't help)  and so on, I'm hoping we've gotten to the bottom
of those.

This does mean we could drop gcc 4.8/4.9 support if we wanted to and
rely on the tarball support for centos7/debian8. I'm torn on that, we
are still missing:

a) Support for wrapping a build with buildtools more auotmatically
(like we do with uninative)

b) documentation of buildtools-extended-tarball

and to drop, we'd probably need these pieces.

I'd note the people who vocally said they needed centos7 support are
not the ones who are doing this work. The only reason I'm pushing it is
I know it will ultimately help support our LTS efforts.

Cheers,

Richard