toolchain/52054: src/libexec/ld.elf_so update breaks everything

[davshao%gmail.com@localhost]

>Number:         52054
>Category:       toolchain
>Synopsis:       src/libexec/ld.elf_so update breaks everything
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 09 17:15:00 +0000 2017
>Originator:     David Shao
>Release:        NetBSD 7.99.65
>Organization:
>Environment:
>Description:
The update

Module Name:    src
Date:           Thu Mar  9 00:43:50 UTC 2017

Modified Files:
        src/libexec/ld.elf_so: map_object.c

Log Message:
really unmap the gap between the text and data rather than just removing
all access with mprotect().

possibly breaks everything including trying to rebuild a system with
./build.sh -O ../obj -T ../tools -U -u build or whatever.

Can someone give me straightforward instructions for how to rebuild AND INSTALL only ld having done a previous
./build.sh -O ../obj -T ../tools -U -u release
and then reverting the problematic changes by
cvs -q update -D "March 8, 2017 23:30 UTC" -Pd

Or is the only recourse to obtain a reverted installation set from elsewhere and just reinstall it over one's system from /
>How-To-Repeat:

>Fix: