Latest emsdk fails with Python 3.7.8 on Windows 10

Python isn't my daily driver and I am stuck trying to make `emscripten_npm_install()` be happy on Windows 10, while fighting for encoding problems.

```
PS D:\WebAssembly\emsdk> .\emsdk install latest
Installing SDK 'sdk-releases-upstream-ce0e4a4d1cab395ee5082a60ebb4f3891a94b256-64bit'..
Skipped installing node-12.18.1-64bit, already installed.
Skipped installing python-3.7.4-pywin32-64bit, already installed.
Skipped installing java-8.152-64bit, already installed.
Skipped installing releases-upstream-ce0e4a4d1cab395ee5082a60ebb4f3891a94b256-64bit, already installed.
Running post-install step: npm ci ...
Running post-install step: npm install google-closure-compiler-windows
Traceback (most recent call last):
File "D:\WebAssembly\emsdk/emsdk.py", line 3082, in
sys.exit(main())
File "D:\WebAssembly\emsdk/emsdk.py", line 3062, in main
success = tool.install()
File "D:\WebAssembly\emsdk/emsdk.py", line 1840, in install
return self.install_sdk()
File "D:\WebAssembly\emsdk/emsdk.py", line 1857, in install_sdk
success = emscripten_npm_install(self, os.path.join(emsdk_path(), install_path, 'emscripten'))
File "D:\WebAssembly\emsdk/emsdk.py", line 1286, in emscripten_npm_install
universal_newlines=True)
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 395, in check_output
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 474, in run
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\subprocess.py", line 926, in communicate
File "D:\obj\windows-release\37amd64_Release\msi_python\zip_amd64\cp1252.py", line 23, in decode
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 625: character maps to
```