cd en_US.ISO8859-1/books/fdp-primer && make FORMATS=html
passes
cd en_US.ISO8859-1/htdocs && make
(succeeds until it tries to reference translations, which I don't have in
my partial checkout)
cd: /usr/home/jrm/scm/freebsd/doc/head/en_US.ISO8859-1/htdocs/../../da_DK.ISO8859-1/htdocs: No such file or directory