remove Makefile assignment of MAKE

For systems such as BSD that use gmake, do not set `MAKE=`.

var.mk

@@ -91,7 +91,6 @@ GENSTRINGS= genstrings
 GETOPT= getopt
 GETOPTS= getopts
 GINDENT= gindent
-GNUMAKE= gnumake
 GREP= grep
 GROFF= groff
 GROFFER= groffer
@@ -123,7 +122,6 @@ LINK= link
 LN= ln
 LS= ls
 M4= m4
-MAKE= make
 MAN= man
 MKDIR= mkdir
 MKFIFO= mkfifo