fix: dev: Allow commandline.c to compile on Solaris

commandline.c failed to compile on Solaris because NAME_MAX was
undefined.  Include 'isc/dir.h' which defines NAME_MAX for platforms
that don't define it.

    In file included from commandline.c:54:
    ./include/isc/commandline.h:31:38: error: 'NAME_MAX' undeclared here (not in a function)
       31 | extern char isc_commandline_progname[NAME_MAX];
          |                                      ^~~~~~~~

Merge branch 'mnowak/fix-solaris-commandline-h' into 'main'

See merge request isc-projects/bind9!10524