LD64Dependency: adjust initializer signature

The method signature of Dependency changed in
1fdf69b90382c43493a5f62f0020729289db6c70, however LD64Dependency was
missed in the update. This resulted in failures in merge_repeats(),
which creates many dependency objects using all three arguments.

Library/Homebrew/requirements/ld64_dependency.rb

@@ -4,7 +4,7 @@ require 'dependency'
 # formula is used as gcc's ld in place of the old version
 # that comes with the OS.
 class LD64Dependency < Dependency
-  def initialize(name='ld64', tags=[:build])
+  def initialize(name='ld64', tags=[:build], env_proc=nil)
     @env_proc = proc { ENV.ld64 }
     super
   end