Thanks to this page, I was able to figure this out at last.
Situation: Building world with an alternate obj directory (specifing MAKEOBJDIRPREFIX) works, but installworld fails with the error "install: no such file or directory". Here's the error I was getting:
# make world MAKEOBJDIRPREFIX=/foo/testing/obj [time passes...] -------------------------------------------------------------- >>> Installing everything.. -------------------------------------------------------------- cd /foo/testing/src; make -f Makefile.inc1 install ===> share/info install -o root -g wheel -m 444 dir-tmpl /foo/testing/obj/usr/share/info/dir install:No such file or directory *** Error code 1
The problem, as explained in the link above, is that for the RELENG4 series, is that MAKEOBJDIRPREFIX is an environment_ variable and needs to be set thusly:
# env MAKEOBJDIRPREFIX=/foo/testing/obj make world