Compiling GRASS on a Sun4

  I've run into a problem compiling GRASS on a Sun4 running 4.1.1 . I get
as far as general/gis in the next_step file before it fails. Per instructions
on page 7 of the instlation guide gmake4.0 is on the path.
  Here is the message from the console
********************************************************************************

GISGEN: general/gis - Wed Jul 15 12:49:18 PDT 1992

#################################################################
/geodata2/jac/grass/grass4.0/src/general/gis
  mkdir OBJ.sun4
  make -f OBJ.sun4/make.rules

making /geodata2/jac/grass/grass4.0
rm -f /geodata2/jac/grass/grass4.0
echo '#!/bin/sh' > /geodata2/jac/grass/grass4.0
sh: /geodata2/jac/grass/grass4.0: Is a directory
*** Error code 1
make: Fatal error: Command failed for target `unix'
GISGEN failure at STEP: general/gis

********************************************************************************
and here is the text from the gis/Gmakefile up to where it fails

********************************************************************************

shell=grass$(VERSION_NUMBER)

EXTRA_CFLAGS = -DD_LOCATION_NAME=\"$(DEFAULT_LOCATION)\" -DD_GISDBASE=\"$(DEFAULT_DATABASE)\" -DVERSION_NUMBER=\"'$(VERSION_NUMBER)'\"

all: unix \
     $(ETC)/GIS.sh \
     $(ETC)/gis_set \
     $(ETC)/clean_temp \
     $(ETC)/lock \
     $(ETC)/run \
     $(ETC)/echo \
     $(ETC)/gis_intro

unix:
        @test -d $(UNIX_BIN) || (echo 'UNIX_BIN($(UNIX_BIN))' not found; exit 1)
        @test -w $(UNIX_BIN) || (echo 'UNIX_BIN($(UNIX_BIN))' not writeable; exit 1)
        @echo making $(UNIX_BIN)/$(shell)
        rm -f $(UNIX_BIN)/$(shell)
        echo '#!/bin/sh' > $(UNIX_BIN)/$(shell)
        echo GISBASE=$(GISBASE) >> $(UNIX_BIN)/$(shell)
        echo export GISBASE >> $(UNIX_BIN)/$(shell)
        echo exec '$$'GISBASE/etc/GIS.sh >> $(UNIX_BIN)/$(shell)
        chmod +x $(UNIX_BIN)/$(shell)
        @echo ""

********************************************************************************

the following is from general/gis/OBJ.sun4/make.rules

********************************************************************************

VERSION_NUMBER=4.0
VERSION_DATE=Summer 1991
VERSION_FILE=/geodata2/jac/grass/grass4.0/src/CMD/VERSION
SRC=/geodata2/jac/grass/grass4.0/src
OBJARCH=OBJ.sun4
LIBARCH=LIB.sun4

GISBASE = /geodata2/jac/grass/grass4.0/sun4
UNIX_BIN = /geodata2/jac/grass