[Project] Make legacy Xcode build root support customizable.

CHANGELOG.md

@@ -66,6 +66,8 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [#2912](https://github.com/CocoaPods/CocoaPods/issues/2912)
 
 * Adding Xcode Legacy build location support for default Pods.xcodeproj.
+  It defaults to `${SRCROOT}/../build` but can be changed in a `post_install`
+  hook by using the `Project#symroot=` writer.  
   [Sam Marshall](https://github.com/samdmarshall)
 
 ##### Bug Fixes

lib/cocoapods/project.rb

@@ -17,9 +17,7 @@ module Pod
       @refs_by_absolute_path = {}
       @pods = new_group('Pods')
       @development_pods = new_group('Development Pods')
-      configs = root_object.build_configuration_list.build_configurations
-      settings_for_all_configs = configs.map(&:build_settings)
-      settings_for_all_configs.each { |settings| settings['SYMROOT'] = '${SRCROOT}/../build' }
+      self.symroot = LEGACY_BUILD_ROOT
     end
 
     # @return [PBXGroup] The group for the support files of the aggregate
@@ -37,6 +35,25 @@ module Pod
 
     public
 
+    # @!group Legacy Xcode build root
+    #-------------------------------------------------------------------------#
+
+    LEGACY_BUILD_ROOT = '${SRCROOT}/../build'
+
+    # @param [String] symroot
+    #        The build root that is used when Xcode is configured to not use the
+    #        workspace’s build root. Defaults to `${SRCROOT}/../build`.
+    #
+    # @return [void]
+    #
+    def symroot=(symroot)
+      root_object.build_configuration_list.build_configurations.each do |config|
+        config.build_settings['SYMROOT'] = symroot
+      end
+    end
+
+    public
+
     # @!group Pod Groups
     #-------------------------------------------------------------------------#
 

spec/unit/project_spec.rb

@@ -20,6 +20,21 @@ module Pod
       it 'creates the development Pods group on initialization' do
         @project.development_pods.name.should == 'Development Pods'
       end
+
+      def settings_for_root_configs(key)
+        @project.root_object.build_configuration_list.build_configurations.map do |config|
+          config.build_settings[key]
+        end
+      end
+
+      it 'assigns a SYMROOT to each root build configuration' do
+        @project.symroot = 'some/build/path'
+        settings_for_root_configs('SYMROOT').uniq.should == ['some/build/path']
+      end
+
+      it 'sets a default SYMROOT for legacy Xcode build setups' do
+        settings_for_root_configs('SYMROOT').uniq.should == [Project::LEGACY_BUILD_ROOT]
+      end
     end
 
     #-------------------------------------------------------------------------#