bin/52328: gforth fails to build

[coypu%sdf.org@localhost]

>Number:         52328
>Category:       bin
>Synopsis:       gforth fails to build
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jun 24 11:55:00 +0000 2017
>Originator:     coypu
>Release:        NetBSD 8.99.1
>Organization:
>Environment:
/bin/sh source date: Sat Jun 24 14:44:35 IDT 2017
>Description:
(cd . && m4 -s -Dcondbranch_opt=1 -DSTACK_CACHE_FILE=cache-fast1.vmg -DSTACK_CACHE_REGS=cache-regs1.vmg prim) >prim-fast.b
sleep 1 #should make hpux-workaround unnecessary
GFORTH="./preforth -p ".:~+:."" ./gfgen -fast
sh: +: bad variable name
*** Error code 1

Stop.
make: stopped in /usr/pkgsrc/lang/gforth/work/gforth-0.7.3
*** Error code 1

I don't know what it's trying to do, but it doesn't fail if I use a sh from 6 months ago.
>How-To-Repeat:
cd /usr/pkgsrc/*/gforth; make install
>Fix: