[UmbrellaHeader] Access platform directly over the target

lib/cocoapods/generator/umbrella_header.rb

@@ -18,7 +18,7 @@ module Pod
       #         @see target
       #
       def initialize(target)
-        super(target.target_definition.platform)
+        super(target.platform)
         @target = target
       end
 

lib/cocoapods/target.rb

@@ -110,12 +110,6 @@ module Pod
     #
     attr_accessor :native_target
 
-    # @return [Platform] the platform for this library.
-    #
-    def platform
-      @platform ||= target_definition.platform
-    end
-
     # @return [String] The value for the ARCHS build setting.
     #
     attr_accessor :archs

lib/cocoapods/target/aggregate_target.rb

@@ -30,6 +30,12 @@ module Pod
       c99ext_identifier(label)
     end
 
+    # @return [Platform] the platform for this target.
+    #
+    def platform
+      @platform ||= target_definition.platform
+    end
+
     # @return [Podfile] The podfile which declares the dependency
     #
     def podfile

lib/cocoapods/target/pod_target.rb

@@ -48,6 +48,12 @@ module Pod
       end
     end
 
+    # @return [Platform] the platform for this target.
+    #
+    def platform
+      @platform ||= target_definitions.first.platform
+    end
+
     # @return [Podfile] The podfile which declares the dependency.
     #
     def podfile