Error: redefinition of module 'CFURLSessionInterface' (Compiling my first hello.swift on Windows 10)

Hi,
I'm trying out Swift for the first time and downloaded 5.3.3-dev for Windows 10, and get the following error when running the compiler from a Console prompt ("x64 Native Tools Command Prompt for VS 2019 Preview").

C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\include\CFURLSessionInterface\module.map:1:8: error: redefinition of module 'CFURLSessionInterface'
module CFURLSessionInterface [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\lib\swift\CFURLSessionInterface\module.map:1:8: note: previously defined here
module CFURLSessionInterface [extern_c] [system] {
^

Why is CFURLSessionInterface searched twice, and should this be the case?
Is the Windows.sdk/usr/include directory included via "-sdk" command-line argument?

EDIT: I wiped the Windows.sdk/usr/include directory and now my hello program compiles. Is this directory supposed to be a symlink to Windows.sdk/usr/lib/swift?

Thanks for any hints!

Full run log:

> set SDKROOT=C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk

> set SWIFTFLAGS=-sdk %SDKROOT% -resource-dir %SDKROOT%\usr\lib\swift -I %SDKROOT%\usr\lib\swift -L %SDKROOT%\usr\lib\swift\windows

> swiftc %SWIFTFLAGS% -emit-executable -o Hello.exe Hello.swift
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\include\CFURLSessionInterface\module.map:1:8: error: redefinition of module 'CFURLSessionInterface'
module CFURLSessionInterface [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\lib\swift\CFURLSessionInterface\module.map:1:8: note: previously defined here
module CFURLSessionInterface [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\include\CFXMLInterface\module.map:1:8: error: redefinition of module 'CFXMLInterface'
module CFXMLInterface [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\lib\swift\CFXMLInterface\module.map:1:8: note: previously defined here
module CFXMLInterface [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\include\CoreFoundation\module.map:1:8: error: redefinition of module 'CoreFoundation'
module CoreFoundation [extern_c] [system] {
^
C:\Library\Developer\Platforms\Windows.platform\Developer\SDKs\Windows.sdk\usr\lib\swift\CoreFoundation\module.map:1:8: note: previously defined here
module CoreFoundation [extern_c] [system] {

use set SWIFTFLAGS=-sdk %SDKROOT%

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