QtCreator System Error during startup: python36.dll missing

I installed python-3.8.2 during building Qt 5.12.8 from souce under Windows as mentioned in https://doc.qt.io/qt-5/windows-requirements.html#building-from-source

Therefore I followed the link that is given there to get Python: http://www.python.org/download/

It also noted in the build instructions:

Python - Install Python from the here and add the installation location to your PATH.

So I did during the installtion process.

I also installed clang from https://releases.llvm.org/download.html.

I have chosen version LLVM 10.0.0 as binary prebuild, as creating the docs for Qt 5.12.8 seems to need this. (Remark: building the docs did not work - noted in another bug).

It seem's that after doing this, starting QtCreator has problems to find a specific version of a python DLL.

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lldb.exe - System Error
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The code execution cannot proceed because python36.dll was not found. Reinstalling the program may fix this problem.
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OK  
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However QtCreator starts through anyway.

In the QtCreator binary install folder I found: 

So not python36 but pyhon35.dll?

What might be the problem?