set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON) will break UWP arm builds. The export tool used by cmake only seems to support x86 and x64 obj files and cannot parse arm obj files.

For example, the vcpkg project uses CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS to generate the export symbols for freetype. All builds work except for UWP arm builds. cmake.exe is not able to parse the arm object files.

https://github.com/Microsoft/vcpkg/blob/master/ports/freetype/0001-Support-Windows-DLLs-via-CMAKE_WINDOWS_EXPORT_ALL_SY.patch

Here is a description of the CMAKE_WINDOWS_EXPORT_ALL_SY feature:

https://blog.kitware.com/create-dlls-on-windows-without-declspec-using-new-cmake-export-all-feature/

https://cmake.org/cmake/help/git-master/prop_tgt/WINDOWS_EXPORT_ALL_SYMBOLS.html