Add basic NixOS support about rex HOT 2 OPEN

with (import <nixpkgs> { });
mkShell {
  buildInputs = with perlPackages; [
    FileShareDirInstall
    ParallelForkManager
    StringEscape
    SubOverride
    TestDeep
    TestException
    TestOutput
    TestUseAllModules
    TestWarnings

    rsync
  ];

  checkInputs = [ coreutils ];

  nativeBuildInputs = with pkgs.perlPackages; [
    ParallelForkManager
    installShellFiles

    pkgs.git
    pkgs.perl
    pkgs.rsync
    pkgs.lsb-release
    pkgs.coreutils
  ];

  propagatedBuildInputs = with perlPackages; [
    AWSSignature4
    DataValidateIP
    DevelCaller
    DigestHMAC
    FileLibMagic
    HashMerge
    HTTPMessage
    IOPty
    IOString
    JSONMaybeXS
    LWP
    NetOpenSSH
    NetSFTPForeign
    SortNaturally
    TermReadKey
    TextGlob
    URI
    XMLSimple
    YAML
  ];
}