fix: prevent IndexError in mkconcore.py when arguments are missing (fixes #267)

[GaneshPatil7517]

@pradeeban

Summary

This PR resolves Issue #267 where mkconcore.py crashes with an IndexError when executed without required arguments.

The script accessed sys.argv[1], sys.argv[2], and sys.argv[3] before validating the number of arguments. As a result, running:

python mkconcore.py

produced:

IndexError: list index out of range

instead of a helpful usage message.

Changes Made

• Moved argument length validation (len(sys.argv) < 4) before any access to sys.argv elements
• Added clear usage message with print()
• Added proper exit with non-zero status code (sys.exit(1))
• Removed the now-redundant late validation block
• No changes made to core logic or generation behavior

Behavior After Fix

• Running without arguments now prints usage instructions and exits with code 1
• Valid usage remains completely unaffected

Scope

• Single-file modification: mkconcore.py
• Minimal, focused change
• No impact on concore-lite, Verilog, or any other modules

[Copilot]

Pull request overview

This PR fixes Issue #267 where mkconcore.py crashes with an IndexError when run without required command-line arguments. The script was accessing sys.argv[1], sys.argv[2], and sys.argv[3] before validating the argument count, causing crashes instead of displaying helpful usage information.

Changes:

• Moved argument validation check (len(sys.argv) < 4) from line 157 to line 109, before any sys.argv access
• Added usage message that displays when arguments are missing
• Removed redundant late validation block that was unreachable

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[pradeeban]

Looks like many lines are changed without reason in addition to the actual change. Can you pls recreate the PR with the least number of lines changed? Probably this is a lone break change in many lines?

The minimal line changes will help avoid merge conflicts and maintain the actual author when a line was not really changed (helps with "git blame")