Merge pull request #8449 from reitermarkus/document-system-config

Refactor and document `SystemConfig`.

Library/Homebrew/extend/os/linux/system_config.rb

@@ -3,7 +3,7 @@
 require "formula"
 require "os/linux/glibc"
 
-class SystemConfig
+module SystemConfig
   class << self
     def host_glibc_version
       version = OS::Linux::Glibc.system_version

Library/Homebrew/extend/os/mac/system_config.rb

 # frozen_string_literal: true
 
-class SystemConfig
+module SystemConfig
   class << self
     undef describe_java, describe_homebrew_ruby
 

Library/Homebrew/system_config.rb

@@ -5,7 +5,10 @@ require "software_spec"
 require "development_tools"
 require "extend/ENV"
 
-class SystemConfig
+# Helper module for querying information about the system configuration.
+#
+# @api private
+module SystemConfig
   class << self
     def clang
       @clang ||= if DevelopmentTools.installed?