Add support for macOS Sierra 10.12

[legal90]

The template has been copied from macosx-10.11.json .I've verified it with parallels-iso builder - it works fine.

But I'm not sure - should I change guest_os_type value for vmware-iso and virtualbox builders or not. I'd appreciate if someone verifies the template with these builders.

[cheeseplus]

Trying to test this today - got stuck on softwareupdate earlier but hopefully that was just transient.

[legal90]

Yes, softwareupdate might take a while because of updates installation. Have you managed to repeat the build?

[cheeseplus]

@legal90 it never seems to complete at that stage (I've only tried with Parallels builder) and I'm not sure how long I should be waiting before calling it hung - are you giving it tons of resources or anything? what do your build times look like?

[legal90]

No, I use a regular MacBook Air, early 2014.
But yeah, now I can confirm that the build hangs for more than 1h on this step:

==> parallels-iso: Provisioning with shell script: scripts/macosx/update.sh
    parallels-iso: + softwareupdate --install --all
    parallels-iso: Software Update Tool
    parallels-iso: Copyright 2002-2015 Apple Inc.
    parallels-iso:
    parallels-iso: Finding available software
    parallels-iso:
    parallels-iso: Downloading macOS Sierra Update
    parallels-iso: Downloading iTunes

and there is no progress for a very long time. Probably, it makes sense to try to rebuild the source .dmg and remove all the redundant stuff like iTunes from there...
Don't know how to check what's actually happening inside 😞

[cheeseplus]

Superseded by #715 but as always the contributions are welcome @legal90