Add Specification#requires_arc shortcut to add -fobj-arc compiler flag.

lib/cocoapods/specification.rb

@@ -106,10 +106,14 @@ module Pod
       @header_dir || pod_destroot_name
     end
 
-    def compiler_flags=(flags)
-      @compiler_flags = flags
+    attr_accessor :requires_arc
+
+    attr_writer :compiler_flags
+    def compiler_flags
+      flags = "#{@compiler_flags} "
+      flags << '-fobj-arc' if @requires_arc
+      flags
     end
-    attr_reader :compiler_flags
 
     # Not attributes
 

spec/unit/specification_spec.rb

@@ -123,6 +123,14 @@ describe "A Pod::Specification loaded from a podspec" do
   it "never equals when it's from a Podfile" do
     Pod::Spec.new.should.not == Pod::Spec.new
   end
+
+  it "adds compiler flags if ARC is required" do
+    @spec.requires_arc = true
+    @spec.compiler_flags.should == " -fobj-arc"
+
+    @spec.compiler_flags = "-Wunused-value"
+    @spec.compiler_flags.should == "-Wunused-value -fobj-arc"
+  end
 end
 
 describe "A Pod::Specification that's part of another pod's source" do