libpar2 fails with clang

See https://github.com/mxcl/homebrew/issues/11926

Formula/libpar2.rb

@@ -8,6 +8,13 @@ class Libpar2 < Formula
   depends_on 'pkg-config' => :build
   depends_on 'libsigc++'
 
+  fails_with :clang do
+    build '318'
+    cause <<-EOS.undent
+      ./par2fileformat.h:87:25: error: flexible array member 'entries' of non-POD element type 'FILEVERIFICATIONENTRY []'
+    EOS
+  end
+
   def install
     system "./configure", "--disable-debug", "--disable-dependency-tracking",
                           "--prefix=#{prefix}"