Add current Ruby globals.

Allows access to the Ruby path. Needed for Linux
porting.

Library/Homebrew/extend/fileutils.rb

@@ -81,13 +81,11 @@ module FileUtils extend self
     end
   end
 
-  RUBY_BIN = '/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin'
-
   def rake *args
-    system "#{RUBY_BIN}/rake", *args
+    system RUBY_BIN/'rake', *args
   end
 
   def ruby *args
-    system "#{RUBY_BIN}/ruby", *args
+    system RUBY_PATH, *args
   end
 end

Library/Homebrew/formula_installer.rb

@@ -285,7 +285,7 @@ class FormulaInstaller
       begin
         read.close
         exec '/usr/bin/nice',
-             '/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby',
+             RUBY_PATH,
              '-W0',
              '-I', Pathname.new(__FILE__).dirname,
              '-rbuild',

Library/Homebrew/global.rb

@@ -7,6 +7,7 @@ require 'extend/object'
 require 'utils'
 require 'exceptions'
 require 'set'
+require 'rbconfig'
 
 ARGV.extend(HomebrewArgvExtension)
 
@@ -63,6 +64,10 @@ end
 
 HOMEBREW_LOGS = Pathname.new('~/Library/Logs/Homebrew/').expand_path
 
+RUBY_CONFIG = RbConfig::CONFIG
+RUBY_BIN = Pathname.new("#{RUBY_CONFIG['bindir']}")
+RUBY_PATH = RUBY_BIN/RUBY_CONFIG['ruby_install_name'] + RUBY_CONFIG['EXEEXT']
+
 if RUBY_PLATFORM =~ /darwin/
   MACOS_FULL_VERSION = `/usr/bin/sw_vers -productVersion`.chomp
   MACOS_VERSION = /(10\.\d+)(\.\d+)?/.match(MACOS_FULL_VERSION).captures.first.to_f