Symlink sources when generating the project. This is useful if you're changing source files inside the generated project and want to bring the changes back into your Unity project or a package.
This option affects sources in both Unity projects and packages.
Only the following platforms support this option:
iOS: When symlinkSources is enabled, Unity creates symlinks for libraries (libil2cpp.a, libiPhone-lib.a, etc.). This means you don't need to copy the libraries. Sources with .mm, .m, .cpp, .c, .h, .swift, and .xib extensions are referenced externally from Xcode project.
Android: When symlinkSources is enabled, Gradle project references .java, .kt and .androidlib plug-in sources externally from Unity project rather than copying the source files directly into the Gradle project. In case of .androidlib plug-in, the plug-in folder must include build.gradle file for the symlinkSources option to work.
Additional resources: BuildPipeline.BuildPlayer, EditorUserBuildSettings.symlinkSources.