[Installer] Create FileAccessors only once per each PodTarget

By iterating over the uniq pod targets, instead of all pod targets per aggregate target, where now the same PodTarget can occur multiple times.

lib/cocoapods/installer.rb

@@ -262,8 +262,7 @@ module Pod
     #       created by the Pod source installer as well.
     #
     def create_file_accessors
-      aggregate_targets.each do |target|
-        target.pod_targets.each do |pod_target|
+      pod_targets.each do |pod_target|
         pod_root = sandbox.pod_dir(pod_target.root_spec.name)
         path_list = Sandbox::PathList.new(pod_root)
         file_accessors = pod_target.specs.map do |spec|
@@ -273,7 +272,6 @@ module Pod
         pod_target.file_accessors.concat(file_accessors)
       end
     end
-    end
 
     # Downloads, installs the documentation and cleans the sources of the Pods
     # which need to be installed.