/usr/src/Makefile target to create an 'installed' subtree ?

For some experiments (with qemu, diskless, jails etc.) i would
like to build an 'installed' subtree from sources, where by
'installed' i mean fully populated including the files in /etc

I see that the 'installworld' and 'installkernel' targets
do part of the work.
'install' (run after installworld) does another part (manpages ?)
but i could not find a way to populate /etc . I tried with
mergemaster and the -m and -D options, but it seems to want a
'make' version that matches the source tree.
Maybe some shell magic involving the following

	MAKE=`make -f Makefile -V BINMAKE` \
	mergemaster -m /sources_are_here/usr/src/etc -D /destination_is_here

(with a few `eval` here and there) can do the job, but i wonder
if there isn't a better option or something already in the
source tree that does not require mergemaster ?

	thanks
	luigi