Enable scl mode for anvil

Registered by Pranesh

One use case is that openstack packages (and their deps) be in pythonX, but system python is python Y (Y!=X). A way to do this is to use software collections (https://access.redhat.com/documentation/en-US/Red_Hat_Software_Collections/).

Building an rpm for use in software collections is slightly different, so anvil has to do a bunch of steps for this. The way I envision this is:
1. smithy takes an extra flag at bootstrap step and intsalls packages needed for scl builds
2. py2rpm needs to know to generate rpms for scl
3. Top level rpmspecs must be configurable (scl vs traditional spec)

Blueprint information

Status:
Not started
Approver:
None
Priority:
Undefined
Drafter:
Pranesh
Direction:
Needs approval
Assignee:
Pranesh
Definition:
New
Series goal:
None
Implementation:
Unknown
Milestone target:
None

Related branches

Sprints

Whiteboard

Gerrit topic: https://review.openstack.org/#q,topic:bp/build-rpms-for-scl,n,z

Addressed by: https://review.openstack.org/110135
    Modify py2rpm to build for scl

Addressed by: https://review.openstack.org/110158
    Modify the bootstrap process to accomodata scl packaging

Addressed by: https://review.openstack.org/120354
    Use spec2scl to postprocess spec files

(?)

Work Items

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