This is an issue when using the new build system in XCode 12 and 13. Any non-trivial project fails to clean after building, as the new build system will refuse to delete a folder in the build tree. Tested in CMake 3.19 and CMake 3.21.1 ``` $ cmake --build . --target clean Command line invocation: /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -project clean_test.xcodeproj clean -target ALL_BUILD -parallelizeTargets -configuration Debug -hideShellScriptEnvironment User defaults from command line: HideShellScriptEnvironment = YES note: Using new build system note: Building targets in parallel warning: Refusing to delete `/tmp/Code/cmake/clean_test/build` because it contains one of the projects in this workspace: `/tmp/Code/cmake/clean_test/build/clean_test.xcodeproj`. error: Could not delete `/tmp/Code/cmake/clean_test/build/test_app` because it was not created by the build system. warning: Refusing to delete `/tmp/Code/cmake/clean_test/build` because it contains one of the projects in this workspace: `/tmp/Code/cmake/clean_test/build/clean_test.xcodeproj`. ** CLEAN FAILED ** ``` Project that reproduces the issue: [clean_test.zip](/uploads/95c6b7f301b15840d7eacb45dd05705f/clean_test.zip)