Remove the universal accessor from BuildOptions

BuildOptions is now immutable (finally).

Library/Homebrew/build_options.rb

@@ -1,6 +1,4 @@
 class BuildOptions
-  attr_accessor :universal
-
   def initialize(args, options)
     @args = args
     @options = options
@@ -48,7 +46,7 @@ class BuildOptions
 
   # True if the user requested a universal build.
   def universal?
-    universal || include?("universal") && option_defined?("universal")
+    include?("universal") && option_defined?("universal")
   end
 
   # True if the user requested to enable C++11 mode.

Library/Homebrew/compat/formula.rb

@@ -43,4 +43,8 @@ class Formula
   def self.factory(name)
     Formulary.factory(name)
   end
+
+  def self.require_universal_deps
+    define_method(:require_universal_deps?) { true }
+  end
 end

Library/Homebrew/formula.rb

@@ -248,6 +248,10 @@ class Formula
     self.class.cxxstdlib.include?(:skip)
   end
 
+  def require_universal_deps?
+    false
+  end
+
   # yields self with current working directory set to the uncompressed tarball
   def brew
     validate_attributes :name, :version
@@ -759,10 +763,6 @@ class Formula
       end
     end
 
-    def require_universal_deps
-      specs.each { |spec| spec.build.universal = true }
-    end
-
     def test &block
       return @test unless block_given?
       @test_defined = true

Library/Homebrew/formula_installer.rb

@@ -310,7 +310,7 @@ class FormulaInstaller
   def inherited_options_for(dep)
     inherited_options = Options.new
     u = Option.new("universal")
-    if (options.include?(u) || f.build.universal?) && !dep.build? && dep.to_formula.option_defined?(u)
+    if (options.include?(u) || f.require_universal_deps?) && !dep.build? && dep.to_formula.option_defined?(u)
       inherited_options << u
     end
     inherited_options