release: Support r/o /usr/ports for cloudware

Set WRKDIRPREFIX=/tmp/ports DISTDIR=/tmp/distfiles when building tools
needed for uploading cloudware images.

While I'm here, adjust the bsdec2-image-upload build target to match
the style used by the Azure/GCE/Vagrant Makefiles.

MFC after: 3 days

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

release: Move the vagrant.vmx config out to its own file to match vbox

Silly to have all these echos and makes this easier to use in other tooling.

Reviewed by: gjb (re)

release: sprinkle UNAME_r hacks following c883b6fd8ccd

Pass UNAME_r override to make(1) for ports builds when building
ports for another branch.

MFC after: 3 days
MFC with: 0be274d37379, 80ab50e1de19, c883b6fd8ccd
Sponsored by: Rubicon Communications, LLC ("Netgate")

release: update to use git instead of svn:

Makefile.* (cloudware):
- Consistify setting the BUILDDATE for snapshots.
(Missed a spot)

Sponsored by: Rubicon Communications, LLC (netgate.com)

Add some comments with examples on how to build Vagrant images.

Approved by: re (gjb)

Add a new vagrant-box target, to make it easier and less redundant to only
produce the Vagrant box and not upload it.

Approved by: re (gjb)

Remove '-' separating OSRELEASE and SNAPSHOT_DATE for vagrant
builds, and prepend it to SNAPSHOT_DATE to prevent a trailing '-'
in the final box name for a release build.

MFC after: 3 days
Sponsored by: The FreeBSD Foundation

Add support for building VirtualBox Vagrant images.
Abstract the build, package and upload to handle building either type.

Approved by: re (gjb)

Remove the HH-MM suffix from the build date suffix.

It was useful when working out several kinks when
testing automated image uploading when retrying was
necessary, but now it is making things much too messy.

MFC after: 3 days
Sponsored by: The FreeBSD Foundation

Default the VAGRANT_VERSION to ${REVISION}-${BRANCH} if
not set, which expands to '11.0-CURRENT', for example.

If the branch is -CURRENT, -STABLE, or -PRERELEASE, suffix
the VAGRANT_VERSION with the snapshot date.

MFC after: 3 days
X-MFC-Needs: r284893, r284895, r284896, r284897, r284942
Tested with: head@r284961 (patched)
Sponsored by: The FreeBSD Foundation

Add Support for uploading Vagrant images to Hashicorp Atlas.

Approved by: re (gjb)

Instead of hard-coding the PROVIDERS for upload, add the
VAGRANT_PROVIDERS variable. Right now, it defaults to only
vmware_desktop, virtualbox support is to follow at some point.

While here, fix the hashicorp URL: s/vagrant/atlas/, which
was result of a sed(1) replace (and my fault).

Sponsored by: The FreeBSD Foundation

Remove _ACCOUNT and add _USERNAME, _NAME, _VERSION for the
VAGRANT_${VAR} variables extracted from VAGRANT_UPLOAD_CONF.

Set ATLAS_${VAR} to VAGRANT_${VAR} if VAGRANT_UPLOAD_CONF
is set. There is intent to intentionally have separate
variants of configuration entries, but the defaults do not
yet have any reason to be different.

Sponsored by: The FreeBSD Foundation

Add default VAGRANT_IMG variable.

Sponsored by: The FreeBSD Foundation

Add initial support for building Vagrant images for VMWare. Next steps will be adding Virtualbox support and uploading to Hashicorp Atlas for others to consume.

Approved by: re (gjb)