add more fallback values to allow basic build to proceed

sys/unix/Makefile.src

@@ -188,7 +188,9 @@ SYSOBJ = $(TARGETPFX)ioctl.o $(TARGETPFX)unixmain.o $(TARGETPFX)unixtty.o \
 #CFLAGS = -O -I../include
 #LFLAGS =
 
+#fallback values, only if these are not already set
 CFLAGS ?= -I../include
+LINK ?= $(CC)
 
 AR = ar
 ARFLAGS = rcs
@@ -408,6 +410,10 @@ WINCURSESLIB = -lncurses
 #
 # LIBS =
 
+#fallback values, only if these are not already set
+WINOBJ ?= $(WINTTYOBJ)
+WINLIB ?= $(WINTTYLIB) -lncurses
+
 # make NetHack
 GAME     = nethack
 # GAME     = nethack.prg

sys/unix/Makefile.utl

@@ -106,6 +106,7 @@ NHSROOT=..
 #CFLAGS = -O -I../include
 #LFLAGS =
 
+#fallback defaults if not set
 CFLAGS ?= -I../include
 
 # -lm required by lua