pkg/55900: go14 bootstrap timestamp issues

[mlelstv%serpens.de@localhost]

>Number:         55900
>Category:       pkg
>Synopsis:       go14 bootstrap timestamp issues
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Dec 31 14:30:01 +0000 2020
>Originator:     Michael van Elst
>Release:        NetBSD 9.0_STABLE
>Organization:
	
>Environment:
	
	
System: NetBSD victory.netbsd.org 9.0_STABLE NetBSD 9.0_STABLE (GENERIC64) #5: Tue Oct 6 21:07:14 CEST 2020 mlelstv@gossam:/home/netbsd9/obj.evbarm64-el/home/netbsd9/src/sys/arch/evbarm/compile/GENERIC64 evbarm
Architecture: aarch64
Machine: evbarm
>Description:
Building go115 with the go14 bootstrap package fails when the
go14 bootstrap was installed from a binary package.

In that case go14 may try to partially rebuild itself, e.g.:

  go install runtime/pprof: open /usr/pkg/go14/pkg/netbsd_arm/runtime/pprof.a: permission denied

go determines if a library (.a file) is stale in relation to another
library by checking the timestamp of the file. The files need timestamps
that correspond to the dependencies of the libraries.

This works fine if go14 is installed from source as the files are built
and written in the correct order.

But installing go14 from a binary package fails because files aren't
extracted from the package in built order.

>How-To-Repeat:
Build go115 but install go14 from a binary package.
>Fix:
Teach go to either evaluate dependencies against sources or to
skip the self-rebuilding completely, in particular when it is
effectively installed read-only.

>Unformatted: