system_config.rb: show system Ruby info on Linux

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

@@ -4,6 +4,7 @@ require "formula"
 require "os/linux/glibc"
 
 module SystemConfig
+  SYSTEM_RUBY_PATH = "/usr/bin/ruby"
   class << self
     def host_glibc_version
       version = OS::Linux::Glibc.system_version
@@ -27,12 +28,20 @@ module SystemConfig
       "N/A"
     end
 
+    def system_ruby_version
+      out, _, status = system_command(SYSTEM_RUBY_PATH, args: ["-e", "puts RUBY_VERSION"], print_stderr: false)
+      return "N/A" unless status.success?
+
+      out
+    end
+
     def dump_verbose_config(out = $stdout)
       dump_generic_verbose_config(out)
       out.puts "Kernel: #{`uname -mors`.chomp}"
       out.puts "OS: #{OS::Linux.os_version}"
       out.puts "Host glibc: #{host_glibc_version}"
       out.puts "/usr/bin/gcc: #{host_gcc_version}"
+      out.puts "/usr/bin/ruby: #{system_ruby_version}" if RUBY_PATH != SYSTEM_RUBY_PATH
       ["glibc", "gcc", "xorg"].each do |f|
         out.puts "#{f}: #{formula_linked_version f}"
       end