Fixed no such file/directory error when running Bash scripts on Windows

[fktn-k]

When the Bash scripts for running clang-format and amalagamation on Windows, they ends up with errors which says no such file/directory.
This is because (1) Python distributions for Windows have no python3 executable and (2) binaries are stored in the venv\Scripts directory, not in the venv/bin directory, when Python venv module is used on Windows.
To fix the above issues, this PR has added platform switches using the output from the uname command.
Both on Ubuntu22.04 with WSL2 and Windows10 with Git for Windows (2.44.0-windows.1), the scripts now work as expected.

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