Fix libmusicbrainz

* Remove optional dep on missing formula.
* Fix neon detection.

Formula/libmusicbrainz.rb

@@ -1,15 +1,17 @@
 require 'formula'
 
 class Libmusicbrainz <Formula
-  @url='http://ftp.musicbrainz.org/pub/musicbrainz/libmusicbrainz-3.0.2.tar.gz'
-  @homepage='http://musicbrainz.org'
-  @md5='648ecd43f7b80852419aaf73702bc23f'
+  url 'http://ftp.musicbrainz.org/pub/musicbrainz/libmusicbrainz-3.0.2.tar.gz'
+  homepage 'http://musicbrainz.org'
+  md5 '648ecd43f7b80852419aaf73702bc23f'
 
   depends_on 'neon'
-  depends_on 'libdiscid' => :optional
 
   def install
-    system "cmake . #{std_cmake_parameters}"
+    neon = Formula.factory("neon")
+    neon_args = "-DNEON_LIBRARIES:FILEPATH=#{neon.lib}/libneon.dylib -DNEON_INCLUDE_DIR:PATH=#{neon.include}/neon"
+
+    system "cmake . #{std_cmake_parameters} #{neon_args}"
     system "make install"
   end
 end