port-amd64/42702: ./build.sh release with some options in mk.conf fail!

[eau%phear.org@localhost]

>Number:         42702
>Category:       port-amd64
>Synopsis:       ./build.sh release  with some options in mk.conf fail!
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jan 30 09:40:00 +0000 2010
>Originator:     Eric Auge
>Release:        netbsd 5.0.1
>Organization:
>Environment:
NetBSD foobsd.no.phear.org 5.0.1 NetBSD 5.0.1 (GENERIC) #0: Thu Jul 30 00:08:07 
UTC 2009 
builds%b7.netbsd.org@localhost:/home/builds/ab/netbsd-5-0-1-RELEASE/amd64/200907292356Z-obj/home/builds/ab/netbsd-5-0-1-RELEASE/src/sys/arch/amd64/compile/GENERIC
 amd64
>Description:
build.sh -m amd64 release cleaned and rebuilt from scratch fails with the 
following issue:

[...]
chmod +w bootxx.amd64
/usr/src/../amd64.tools/bin/nbinstallboot -mamd64 -e -o console=com0 
bootxx.amd64
nbinstallboot: Invalid magic in exiting bootstrp
nbinstallboot: Edit bootstrap operation failed
*** Failed command: /usr/src/../amd64.tools/bin/nbinstallboot -mamd64 -e -o 
console=com0 bootxx.amd64
*** Error code 1

Stop.
nbmake: stopped in /usr/src/distrib/amd64/cdroms/bootcd-com

*** Failed target: release-bootcd-com
*** Failed command: _makedirtarget() { dir="$1"; shift; target="$1"; case 
"${dir}" in /*) this="${dir}/"; real="${dir}" ;; .) this="etc/amd64/cdroms/"; 
real="/usr/src/distrib/amd64/cdroms" ;; *) this="etc/amd64/cdroms/${dir}/"; 
real="/usr/src/distrib/amd64/cdroms/${dir}" ;; esac; show=${this:-.}; echo 
"${target} ===> ${show%/}${1:+ (with: $@)}"; cd "${real}" && 
/usr/src/../amd64.tools/bin/nbmake _THISDIR_="${this}" "$@" ${target}; }; 
_makedirtarget bootcd-com release
*** Error code 1

Stop.
[...]
>How-To-Repeat:
my mk.conf is the following:

MKDOC=yes
MKDYNAMICROOT=yes
MKGCC=yes
MKGCCCMDS=yes
MKGDB=yes
MKHESIOD=yes
MKMAN=yes
MKHTML=yes
MKPIE=yes
MKSKEY=yes
MKIPFILTEr=no
MKYP=no
MKSTRIPIDENT=yes
USE_SSP=yes


and i do the following 
cd /usr/src
./build.sh -m amd64 -T ../amd64.tools -O ../amd64.obj -R ../amd64.release 
release

This is running in a virtualbox vm, i use it for cross compiling systems for 
updating various box on different arch (cobalt/macppc/sparc64/amd64)


>Fix: