The error:

Making install in pro-engineer
make[2]: Entering directory `/var/tmp/portage/brlcad-7.0.2/work/brlcad-7.0/misc/pro-engineer'
make[3]: Entering directory `/var/tmp/portage/brlcad-7.0.2/work/brlcad-7.0/misc/pro-engineer'
make[3]: Nothing to be done for `install-exec-am'.
/bin/sh ../../misc/mkinstalldirs /usr/lib/../pro-engineer
 /bin/install -c -m 644 install.doc /usr/lib/../pro-engineer/install.doc
ACCESS DENIED  unlink:    /usr/pro-engineer/install.doc
/bin/install: cannot remove `/usr/lib/../pro-engineer/install.doc': Permission denied
 /bin/install -c -m 644 protk.dat /usr/lib/../pro-engineer/protk.dat
ACCESS DENIED  unlink:    /usr/pro-engineer/protk.dat
/bin/install: cannot remove `/usr/lib/../pro-engineer/protk.dat': Permission denied
make[3]: *** [install-proeDATA] Error 1
make[3]: Leaving directory `/var/tmp/portage/brlcad-7.0.2/work/brlcad-7.0/misc/pro-engineer'
make[2]: *** [install-am] Error 2
make[2]: Leaving directory `/var/tmp/portage/brlcad-7.0.2/work/brlcad-7.0/misc/pro-engineer'
make[1]: *** [install-recursive] Error 1
make[1]: Leaving directory `/var/tmp/portage/brlcad-7.0.2/work/brlcad-7.0/misc'
make: *** [install-recursive] Error 1

The apparent offender:

install-proeDATA: $(proe_DATA)
        @$(NORMAL_INSTALL)
        $(mkinstalldirs) $(DESTDIR)$(proedir)
        @list='$(proe_DATA)'; for p in $$list; do \
          if test -f "$$p"; then d=; else d="$(srcdir)/"; fi; \
          f="`echo $$p | sed -e 's|^.*/||'`"; \
          echo " $(proeDATA_INSTALL) $$d$$p $(DESTDIR)$(proedir)/$$f"; \
          $(proeDATA_INSTALL) $$d$$p $(DESTDIR)$(proedir)/$$f; \
        done

in brlcad-7.0/misc/pro-engineer/Makefile

Not sure how to make this behave properly.