nbawk: non-terminated string echo x86_6... at source line 73

[Andrew Cagney <andrew.cagney%gmail.com@localhost>]

Seeing below; happens for at least arm and amd64:

===> build.sh command:    ./build.sh -m amd64 -u -U -N 3 -j1 -O
/home/netbsd/hg/amd64 -T /home/netbsd/hg/tools release install-image
live-image
===> build.sh started:    Mon Nov 20 19:51:41 EST 2017
===> NetBSD version:      8.99.6
===> MACHINE:             amd64
===> MACHINE_ARCH:        x86_64
===> Build platform:      Linux 4.13.13-200.fc26.x86_64 x86_64
===> HOST_SH:             /usr/bin/sh
===> No $TOOLDIR/bin/nbmake, needs building.
===> Bootstrapping nbmake
....
cd /home/netbsd/hg/src/distrib/sets &&
DESTDIR=/home/netbsd/hg/amd64/destdir.amd64  MACHINE=amd64
MACHINE_ARCH=x86_64  AWK=/home/netbsd/hg/tools/bin/nbawk
CKSUM=/home/netbsd/hg/tools/bin/nbcksum
DB=/home/netbsd/hg/tools/bin/nbdb  EGREP=grep\ -E  HOST_SH=/usr/bin/sh
 MAKE=/home/netbsd/hg/tools/bin/nbmake
MKTEMP=/home/netbsd/hg/tools/bin/nbmktemp
MTREE=/home/netbsd/hg/tools/bin/nbmtree
PAX=/home/netbsd/hg/tools/bin/nbpax  COMPRESS_PROGRAM=gzip  GZIP=-n
PKG_CREATE=/home/netbsd/hg/tools/bin/nbpkg_create
SED=/home/netbsd/hg/tools/bin/nbsed
TSORT=/home/netbsd/hg/tools/bin/nbtsort\ -q  /usr/bin/sh ./maketars -S
-d /home/netbsd/hg/amd64/destdir.amd64   -M
/home/netbsd/hg/amd64/destdir.amd64/METALOG.sanitised  -N
/home/netbsd/hg/src/etc -L base -t
/home/netbsd/hg/amd64/releasedir/amd64/binary/sets
/home/netbsd/hg/tools/bin/nbawk: non-terminated string echo x86_6...
at source line 73
 context is
                    wanted["machine_cpu=" "echo x86_64 >>>
 <<<
DEBUG: list_set_files: ./lists/base/mi
DEBUG: list_set_files: ./lists/base/md.amd64
DEBUG: list_set_files: ./lists/base/shl.mi
DEBUG: list_set_files: ./lists/base/module.mi
DEBUG: list_set_files: ./lists/base/rescue.mi
xargs: /home/netbsd/hg/tools/bin/nbsed: terminated by signal 13

The code in sets.subr seems to be:

            if ("machine_cpu" in wanted)
                wanted["machine_cpu=" "'"${MACHINE_CPU}"'"] = 1

any ideas