toolchain/52804: make postinstall obsoletelibs a separate thing?

[dholland%NetBSD.org@localhost]

>Number:         52804
>Category:       toolchain
>Synopsis:       make postinstall obsoletelibs a separate thing?
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    toolchain-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 10 05:15:00 +0000 2017
>Originator:     David A. Holland
>Release:        NetBSD 8.99.8 (20171205)
>Organization:
>Environment:
System: NetBSD valkyrie 8.99.8 NetBSD 8.99.8 (VALKYRIE) #24: Tue Dec  5 17:30:57 EST 2017  dholland@valkyrie:/usr/src/sys/arch/amd64/compile/VALKYRIE amd64
Architecture: x86_64
Machine: amd64
>Description:

It occurred to me tonight while working on unborking a machine that
was running a mixture of 6.1 and 7.99.33 that it would be useful to be
able to run subsets of "postinstall fix obsolete", so as to allow
clearing away the bulk of the obsolete files while leaving dangerous
ones or suspect ones for closer analysis.

But I think it would be sufficient to just split the obsolete library
handling apart from the obsolete paths handling and make them separate
toplevel targets. As far as I know the downgrade hazards associated
with postinstall fix obsolete are limited to shared library images.

>How-To-Repeat:

>Fix: