Add syslog as runtime dependency

The syslog gem moves from default gems to a normal gem in Ruby 3.4. It
raises the following warning on Ruby 3.3.5:

```
lib/puppet/util/command_line.rb:14: warning: syslog was loaded from the standard library, but will no longer be part of the default gems starting from Ruby 3.4.0.
You can add syslog to your Gemfile or gemspec to silence this warning.
```

Gemfile

@@ -35,7 +35,6 @@ group(:features) do
   # requires native ldap headers/libs
   # gem 'ruby-ldap', '~> 0.9', require: false, platforms: [:ruby]
   gem 'puppetserver-ca', '~> 2.0', require: false
-  gem 'syslog', '~> 0.1.1', require: false, platforms: [:ruby]
   gem 'CFPropertyList', ['>= 3.0.6', '< 4'], require: false
 end
 

puppet.gemspec

@@ -41,4 +41,8 @@ Gem::Specification.new do |spec|
     spec.add_runtime_dependency('ffi', '>= 1.15.5', '< 1.17.0', '!= 1.16.0', '!= 1.16.1', '!= 1.16.2')
     spec.add_runtime_dependency('minitar', '~> 0.9')
   end
+
+  if platform == 'x86_64-linux'
+    spec.add_runtime_dependency('syslog', '~> 0.1.2')
+  end
 end