error messages from including files

[Arthur Davis]

A snippet from a posting to the help-make list on 25 Oct 2002 by Paul
D. Smith:

 $ cat Makefile
 %.mk : %.mk.in ; cp $< $@
 include one.mk
 all:;@echo $(FOO)

 $ cat one.mk.in
 FOO = one
 include two.mk

 $ cat two.mk.in
 FOO = two

 $ make
 Makefile:2: one.mk: No such file or directory
 cp one.mk.in one.mk
 one.mk:2: two.mk: No such file or directory
 cp two.mk.in two.mk
 two

 $ make
 two

Can the two error messages that make prints stating that it can't find
the included make files be supressed?  Could the include be surrounded
with a conditional of some sort that would check and build the included
files when needed?  I unsuccessfully tried different variations of the
following:

ifeq ($(shell test -f one.mk || echo no),)
include one.mk
else
<different things here - none worked>
endif

I've also tried to come up with a rule that would solve this, but
haven't had any success.  Any suggestions?  Am I close?  Can it be dome?