[Installer] Fix architecture determination

lib/cocoapods/installer/analyzer.rb

@@ -369,7 +369,7 @@ module Pod
         if config.integrate_targets?
           target_inspections = result.target_inspections.select { |t, _| target_definitions.include?(t) }.values
           pod_target.user_build_configurations = target_inspections.map(&:build_configurations).reduce({}, &:merge)
-          pod_target.archs = target_inspections.map(&:archs).uniq.sort
+          pod_target.archs = target_inspections.flat_map(&:archs).compact.uniq.sort
         else
           pod_target.user_build_configurations = {}
           if target_definitions.first.platform.name == :osx
@@ -651,7 +651,10 @@ module Pod
         inspection_result = {}
         UI.section 'Inspecting targets to integrate' do
           podfile.target_definition_list.each do |target_definition|
-            inspection_result[target_definition] = TargetInspector.new(target_definition).inspect!
+            results = TargetInspector.new(target_definition).inspect!
+            inspection_result[target_definition] = results
+            UI.message('Using `ARCHS` setting to build architectures of ' \
+              "target `#{target_definition.label}`: (`#{results.archs.join('`, `')}`)")
           end
         end
         inspection_result

lib/cocoapods/installer/analyzer/target_inspector.rb

@@ -155,14 +155,9 @@ module Pod
         # @return [Array<String>]
         #
         def compute_archs(user_targets)
-          archs = user_targets.flat_map do |target|
+          user_targets.flat_map do |target|
             Array(target.common_resolved_build_setting('ARCHS'))
           end.compact.uniq.sort
-
-          UI.message('Using `ARCHS` setting to build architectures of ' \
-                   "target `#{target_definition.label}`: " \
-                   "(`#{archs.join('`, `')}`)")
-          archs.length > 1 ? archs : archs.first
         end
 
         # Checks if any of the targets for the {TargetDefinition} computed before

lib/cocoapods/installer/target_installer.rb

@@ -67,7 +67,7 @@ module Pod
       def custom_build_settings
         settings = {}
 
-        if target.archs
+        unless target.nil? || target.archs.empty?
           settings['ARCHS'] = target.archs
         end
 

spec/unit/installer/analyzer/target_inspector_spec.rb

@@ -152,7 +152,7 @@ module Pod
         user_targets = [target]
 
         archs = TargetInspector.new(target_definition).send(:compute_archs, user_targets)
-        archs.should == 'armv7'
+        archs.should == %w(armv7)
       end
 
       it 'handles a single ARCH defined in multiple user targets' do
@@ -167,7 +167,7 @@ module Pod
         user_targets = [targeta, targetb]
 
         archs = TargetInspector.new(target_definition).send(:compute_archs, user_targets)
-        archs.should == 'armv7'
+        archs.should == %w(armv7)
       end
 
       it 'handles an Array of ARCHs defined in a single user target' do

spec/unit/installer/analyzer_spec.rb

@@ -100,6 +100,8 @@ module Pod
         ].sort
         target.support_files_dir.should == config.sandbox.target_support_files_dir('Pods')
 
+        target.pod_targets.map(&:archs).uniq.should == [[]]
+
         target.user_project_path.to_s.should.include 'SampleProject/SampleProject'
         target.client_root.to_s.should.include 'SampleProject'
         target.user_target_uuids.should == ['A346496C14F9BE9A0080D870']