config: Print host glibc version [Linux]

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

@@ -1,4 +1,5 @@
 require "formula"
+require "os/linux/glibc"
 
 class SystemConfig
   class << self
@@ -14,6 +15,12 @@ class SystemConfig
       end
     end
 
+    def host_glibc_version
+      version = OS::Linux::Glibc.system_version
+      return "N/A" if version.null?
+      version
+    end
+
     def host_gcc_version
       gcc = Pathname.new "/usr/bin/gcc"
       return "N/A" unless gcc.executable?
@@ -31,6 +38,7 @@ class SystemConfig
       dump_generic_verbose_config(out)
       out.puts "Kernel: #{`uname -mors`.chomp}"
       out.puts "OS: #{host_os_version}"
+      out.puts "Host glibc: #{host_glibc_version}"
       out.puts "/usr/bin/gcc: #{host_gcc_version}"
       ["glibc", "gcc", "xorg"].each do |f|
         out.puts "#{f}: #{formula_linked_version f}"

Library/Homebrew/os/linux/glibc.rb

@@ -0,0 +1,14 @@
+module OS
+  module Linux
+    module Glibc
+      module_function
+
+      def system_version
+        return @system_version if @system_version
+        version = Utils.popen_read("/usr/bin/ldd", "--version")[/ (\d+\.\d+)/, 1]
+        return Version::NULL unless version
+        @system_version = Version.new version
+      end
+    end
+  end
+end