Making ${UOBJS} (containing various "unix/<objectname>.@O@" entries) a
dependency for executable targets and setting SUBDIRS to "unix" in
bin/confgen/Makefile.in and bin/named/Makefile.in causes two issues with
parallel make ("make -jX"):

  - ${UOBJS} may be built in both bin/{confgen,named} and the "unix"
    subdirectory of each of these directories,

  - if building objects inside the "unix" subdirectory is not complete
    by the time linking the targets inside bin/{confgen,named} is
    attempted, an error will occur due to at least one required object
    file not being present, e.g.:

        gcc: error: unix/os.o: No such file or directory