usage ./build.sh [options] command <command options>

 General options:
    -N <iso_name>      Set an iso filename (prefix)
                        Default: archlinux
    -V <iso_version>   Set an iso version (in filename)
                        Default: 2011.08.18
    -L <iso_label>     Set an iso label (disk label)
                        Default: ARCH_201108
    -D <install_dir>   Set an install_dir (directory inside iso)
                        Default: arch
    -w <work_dir>      Set the working directory
                        Default: work
    -o <out_dir>       Set the output directory
                        Default: out
    -v                 Enable verbose output
    -h                 This help message

 Commands:
   build <mode> <type>
      Build selected .iso by <mode> and <type>
   purge <mode>
      Clean working directory except iso/ directory of build <mode>
   clean <mode>
      Clean working directory and .iso file in output directory of build <mode>

 Command options:
         <mode> Valid values 'single' or 'dual'
         <type> Valid values 'netinstall', 'core' or 'all'

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>