makefile: configure with --enable-racket => no 3m dependency CS

Adjust the makefile that ends up in <builddir> with `--enable-cs` or
`--enable-csdefault` (as opposed to `--enable-csonly`) so that `make
racketcs` doesn't imply `make racket3m` if `--enable-racket` has
supplied an existing Racket.

Also fix `make install-cs` related to GRacket for the case that Racket
3m/CGC isn't built.

Relevant to #2683

racket/src/Makefile.in

@@ -134,9 +134,11 @@ install-common-first:
         esac
 	mkdir -p $(ALLDIRINFO)
 
+MIDDLE_POST_COLLECTS = install-@MAKE_GRACKET@-post-collects
+
 install-common-middle:
 	$(MAKE) @MAKE_COPYTREE@-run
-	$(MAKE) install-@MAKE_GRACKET@-post-collects
+	$(MAKE) $(MIDDLE_POST_COLLECTS)
 	$(MAKE) lib-finish
 
 install-common-last:
@@ -259,7 +261,7 @@ CS_SETUP_INSTALL_TARGET = setup-install
 install-cs-common:
 	$(MAKE) install-common-first
 	cd cs/c; $(MAKE) plain-install
-	$(MAKE) install-common-middle
+	$(MAKE) install-common-middle MIDDLE_POST_COLLECTS=install-no-post-collects
 	cd cs/c; $(MAKE) $(CS_SETUP_INSTALL_TARGET)
 	$(MAKE) install-common-last
 

racket/src/cfg-racket

@@ -5054,7 +5054,12 @@ if test "${enable_cgcdefault}" ; then
    MAIN_VARIANT=cgc
 fi
 MAIN_MAKE_TARGET="${MAIN_VARIANT}"
+
+if test "${enable_racket}" = "" ; then
   CS_BOOTSTRAP_HELP="${MAIN_VARIANT}"
+else
+  CS_BOOTSTRAP_HELP="no-${MAIN_VARIANT}"
+fi
 
 if test "${enable_csdefault}" ; then
    MMM_INSTALLED=3m

racket/src/racket/configure.ac

@@ -769,7 +769,12 @@ if test "${enable_cgcdefault}" ; then
    MAIN_VARIANT=cgc
 fi
 MAIN_MAKE_TARGET="${MAIN_VARIANT}"
+
+if test "${enable_racket}" = "" ; then
   CS_BOOTSTRAP_HELP="${MAIN_VARIANT}"
+else
+  CS_BOOTSTRAP_HELP="no-${MAIN_VARIANT}"
+fi
 
 if test "${enable_csdefault}" ; then
    MMM_INSTALLED=3m