[XCConfigHelper] Adds $(inherited) to generated OTHER_SWIFT_FLAGS

[XCConfigHelper] Adds $(inherited) to generated OTHER_SWIFT_FLAGS

CHANGELOG.md

@@ -34,6 +34,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
   [Samuel Giddins](https://github.com/segiddins)
   [#3230](https://github.com/CocoaPods/CocoaPods/issues/3230)
 
+* Fix the `OTHER_SWIFT_FLAGS` generated, so it inherits previous definitions.  
+  [Daniel Thorpe](https://github.com/danthorpe)
+  [#2983](https://github.com/CocoaPods/CocoaPods/issues/2983)
+
 
 ## 0.36.0.rc.1
 

lib/cocoapods/generator/xcconfig/xcconfig_helper.rb

@@ -160,7 +160,7 @@ module Pod
         def self.add_language_specific_settings(target, xcconfig)
           if target.uses_swift?
             build_settings = {
-              'OTHER_SWIFT_FLAGS' => quote(%w(-D COCOAPODS)),
+              'OTHER_SWIFT_FLAGS' => '$(inherited) ' + quote(%w(-D COCOAPODS)),
             }
             xcconfig.merge!(build_settings)
           end

spec/unit/generator/xcconfig/aggregate_xcconfig_spec.rb

@@ -157,7 +157,7 @@ module Pod
           end
 
           it 'adds the COCOAPODS macro definition' do
-            @xcconfig.to_hash['OTHER_SWIFT_FLAGS'].should.include '"-D" "COCOAPODS"'
+            @xcconfig.to_hash['OTHER_SWIFT_FLAGS'].should.include '$(inherited) "-D" "COCOAPODS"'
           end
         end