iOS Build Failure on appending build folder

iOS builds are failing with the below exception.
We are using Unity 2019.4.20f1 & the Append option for the build.

Code (CSharp):

1. Exception: The given path Classes/Unity/IUnityInterface.h does not refer to a file in a known build section
2. UnityEditor.iOS.Xcode.PBXProjectData.BuildSectionAny (UnityEditor.iOS.Xcode.PBX.PBXNativeTargetData target, System.String path, System.Boolean isFolderRef) (at /Users/bokken/buildslave/unity/build/External/XcodeAPI/Xcode/PBXProjectData.cs:250)
3. UnityEditor.iOS.Xcode.PBXProject.BuildSectionAny (UnityEditor.iOS.Xcode.PBX.PBXNativeTargetData target, System.String path, System.Boolean isFolderRef) (at /Users/bokken/buildslave/unity/build/External/XcodeAPI/Xcode/PBXProject.cs:86)
4. UnityEditor.iOS.Xcode.PBXProject.AddBuildFileImpl (System.String targetGuid, System.String fileGuid, System.Boolean weak, System.String compileFlags) (at /Users/bokken/buildslave/unity/build/External/XcodeAPI/Xcode/PBXProject.cs:266)
5. UnityEditor.iOS.Xcode.PBXProject.AddFileToBuildWithFlags (System.String targetGuid, System.String fileGuid, System.String compileFlags) (at /Users/bokken/buildslave/unity/build/External/XcodeAPI/Xcode/PBXProject.cs:295)
6. UnityEditor.iOS.PostProcessiPhonePlayer.BuildXCodeProject (UnityEditor.iOS.PostProcessiPhonePlayer+ProjectPaths paths, UnityEditor.iOS.PostProcessiPhonePlayer+BuildSettings bs, UnityEditor.iOS.PostProcessiPhonePlayer+UsedFeatures usedFeatures, UnityEditor.iOS.PostProcessiPhonePlayer+IncludedFileList includedFiles, System.Collections.Generic.List`1[T] frameworks, System.Collections.Generic.List`1[T] initialInstallTags) (at /Users/bokken/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:2486)
7. UnityEditor.iOS.PostProcessiPhonePlayer.PostProcess (UnityEditor.iOS.PostProcessiPhonePlayer+BuildSettings bs, UnityEditor.iOS.PostProcessiPhonePlayer+ProjectPaths paths, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.Build.Reporting.BuildReport buildReport) (at /Users/bokken/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:817)
8. UnityEditor.iOS.PostProcessiPhonePlayer.PostProcess (UnityEditor.iOS.PostProcessorSettings postProcessorSettings, UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/bokken/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/BuildPostProcessor.cs:679)
9. UnityEditor.iOS.iOSBuildPostprocessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/bokken/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/ExtensionModule.cs:45)
10. Rethrow as BuildFailedException: Exception of type 'UnityEditor.Build.BuildFailedException' was thrown.
11. UnityEditor.iOS.iOSBuildPostprocessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at /Users/bokken/buildslave/unity/build/PlatformDependent/iPhonePlayer/Extensions/Common/ExtensionModule.cs:49)
12. UnityEditor.Modules.DefaultBuildPostprocessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args, UnityEditor.BuildProperties& outProperties) (at /Users/bokken/buildslave/unity/build/Editor/Mono/Modules/DefaultBuildPostprocessor.cs:29)
13. UnityEditor.PostprocessBuildPlayer.Postprocess (UnityEditor.BuildTargetGroup targetGroup, UnityEditor.BuildTarget target, System.String installPath, System.String companyName, System.String productName, System.Int32 width, System.Int32 height, UnityEditor.BuildOptions options, UnityEditor.RuntimeClassRegistry usedClassRegistry, UnityEditor.Build.Reporting.BuildReport report) (at /Users/bokken/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:353)

This issue seems to be similar to
https://issuetracker.unity3d.com/is...ethod-fails-build-when-appending-build-folder
Is there any workaround or fix for it?
We still want to keep the Append build option.

 

This error happens when Unity XCode API is not able to find this header file in PBXHeadersBuildPhase section of XCode workspace. To fix it, need to add that header file in Build Phase (Header Phase) of the XCode project