I've seen this one once or twice before, but it wasn't consistent.
Today, it's happening every time I do a ./build.sh -u ..., but only
for port-amd64;  the same invocation of build.sh for port-i386 does
not have this problem.

#    create  set lists
cd /usr/src/distrib/sets &&  DESTDIR=/usr/obj/destdir.amd64 
MACHINE=amd64 MACHI
NE_ARCH=x86_64  CKSUM=/usr/obj/tools.x86_64.amd64/bin/nbcksum 
DB=/usr/obj/tools
.x86_64.amd64/bin/nbdb  HOST_SH=/bin/sh 
MAKE=/usr/obj/tools.x86_64.amd64/bin/nb
make  MKTEMP=/usr/obj/tools.x86_64.amd64/bin/nbmktemp 
MTREE=/usr/obj/tools.x86_
64.amd64/bin/nbmtree  PAX=/usr/obj/tools.x86_64.amd64/bin/nbpax 
TSORT=/usr/obj/
tools.x86_64.amd64/bin/nbtsort\ -q  /bin/sh ./maketars -S -d 
/usr/obj/destdir.am
d64   -N /usr/src/etc -b -t /usr/obj/reldir/amd64/binary/sets
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
[: all: unexpected operator
<snip> a few dozen more occurrences

Any clues?

----------------------------------------------------------------------
|   Paul Goyette   | PGP DSS Key fingerprint: |  E-mail addresses:   |
| Network Engineer | FA29 0E3B 35AF E8AE 6651 |  paul@whooppee.com   |
|                  | 0786 F758 55DE 53BA 7731 | pgoyette@juniper.net |
----------------------------------------------------------------------