S3Backup: check for bzip2 and xz Nix Config support (Use of uninitialized value ::Config::xz in concatenation)

Dependencies

• [2] UGFTLRWC Delay initializing the s3 client until it's needed to silence warnings
• [3] UGA45FNC Add a plugin for backing up builds in s3
• [4] 5WNGKHLZ Plugins: Add isEnabled method

Change contents

• replacement in src/lib/Hydra/Plugin/S3Backup.pm at line 24
  [2.12]→[3.2087:2195](∅→∅),[3.2087]→[3.2087:2195](∅→∅)
  − my %compressors = (

  − xz => "| $Nix::Config::xz",

  − bzip2 => "| $Nix::Config::bzip2",

  − none => ""

  − );
  [2.12]

  [3.2195]
  + my %compressors = ();

  +

  + $compressors{"none"} = "";

  +

  + if (defined($Nix::Config::bzip2)) {

  + $compressors{"bzip2"} = "| $Nix::Config::bzip2",

  + }

  +

  + if (defined($Nix::Config::xz)) {

  + $compressors{"xz"} = "| $Nix::Config::xz",

  + }

  +