Remove @SET_MAKE@ from manually-maintained files

Emacs now assumes GNU Make, so @SET_MAKE@ is no longer needed.
* Makefile.in, lwlib/Makefile.in, nextstep/Makefile.in:
* src/Makefile.in: Remove @SET_MAKE@.

Makefile.in

@@ -68,9 +68,6 @@ SHELL = @SHELL@
 # current directory.
 CDPATH=
 
-# If Make doesn't predefine MAKE, set it here.
-@SET_MAKE@
-
 # ==================== Things 'configure' Might Edit ====================
 
 cache_file = @cache_file@

lwlib/Makefile.in

@@ -26,7 +26,6 @@ srcdir=@srcdir@
 # MinGW CPPFLAGS may use this.
 abs_top_srcdir=@abs_top_srcdir@
 VPATH=@srcdir@
-@SET_MAKE@
 C_SWITCH_X_SITE=@C_SWITCH_X_SITE@
 C_SWITCH_SYSTEM=@C_SWITCH_SYSTEM@
 C_SWITCH_MACHINE=@C_SWITCH_MACHINE@

nextstep/Makefile.in

@@ -30,7 +30,6 @@ EXEEXT = @EXEEXT@
 # abs_top_srcdir may contain ".."
 top_srcdir_abs = $(shell cd @top_srcdir@; pwd -P)
 
-@SET_MAKE@
 MKDIR_P = @MKDIR_P@
 
 ## Emacs.app.

src/Makefile.in

@@ -38,9 +38,6 @@ CPPFLAGS = @CPPFLAGS@
 LDFLAGS = @LDFLAGS@
 EXEEXT = @EXEEXT@
 version = @version@
-# Substitute an assignment for the MAKE variable, because
-# BSD doesn't have it as a default.
-@SET_MAKE@
 MKDIR_P = @MKDIR_P@
 # Don't use LIBS.  configure puts stuff in it that either shouldn't be
 # linked with Emacs or is duplicated by the other stuff below.