[CMake]: Fix python command for mingw environment (#6984)
[CMake]: Fix python command for mingw environment (#6984)

In mingw build environment, this fixes the build error:
'py' is not recognized as an internal or external command
The 'py' launcher is available for MSVC python only. More
https://docs.python.org/3/using/windows.html#from-the-command-line
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