Add Clang as an option to LLVM formula

Formula/llvm.rb

@@ -1,17 +1,48 @@
 require 'formula'
 
+class Clang <Formula
+  url       'http://llvm.org/releases/2.6/clang-2.6.tar.gz'
+  homepage  'http://llvm.org/'
+  md5       '09d696bf23bb4a3cf6af3c7341cdd946'
+end
+
 class Llvm <Formula
-  @url='http://llvm.org/releases/2.6/llvm-2.6.tar.gz'
-  @homepage='http://llvm.org/'
-  @md5='34a11e807add0f4555f691944e1a404a'
+  url       'http://llvm.org/releases/2.6/llvm-2.6.tar.gz'
+  homepage  'http://llvm.org/'
+  md5       '34a11e807add0f4555f691944e1a404a'
+
+  def options
+    [
+      ['--with-clang', 'Also build & install clang']
+    ]
+  end
+
+  def clang?
+    ARGV.include? '--with-clang'
+  end
 
   def install
     ENV.gcc_4_2 # llvm can't compile itself
 
+    if clang?
+      clang_dir = File.join(Dir.pwd, 'tools', 'clang')
+
+      Clang.new.brew {
+        FileUtils.mkdir_p clang_dir
+        FileUtils.mv Dir['*'], clang_dir
+      }
+    end
+
     system "./configure", "--prefix=#{prefix}",
                           "--enable-targets=host-only",
                           "--enable-optimized"
     system "make"
     system "make install" # seperate steps required, otherwise the build fails
+
+    if clang?
+      Dir.chdir clang_dir do
+        system "make install"
+      end
+    end
   end
 end