- took the 3d tool out of the build list but kept the code in place

3d has become too hard to build
  consider using ndfs which has some of the functionality of 3d

src/cmd/3d/Makefile

@@ -1,3 +1,4 @@
+if CC.HOSTTYPE == "no_build"
 /*
  * 3d fs library
  *
@@ -101,3 +102,9 @@ terminal FEATURE/eaccess FEATURE/hack
 	$(BINDIR)/3d $(SHELL) $(REGRESS) $(REGRESSFLAGS) $(*)
 
 :: sys.tab
+
+else
+
+:NOTHING:
+
+end