Refactor file download error handling

[sweep-ai[bot]]

Description

This PR refactors the error handling in the file download process to provide a more robust and flexible error handling mechanism.

Summary of Changes

• In dl.go:
  • Replaced the panic statement in the DlTo method of the GHReleaseDl struct with an error return. This ensures that errors during the file download process are returned to the caller function instead of abruptly stopping the program execution.
• In ghdl/main.go:
  • Updated the Run function of the rootCmd variable to handle the error returned by the DlTo method. If an error is returned, an error message is printed and the program exits with a non-zero status code.

These changes improve the code's reliability and maintainability by providing a more controlled and predictable error handling mechanism.

Fixes #3.

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[beetcb]

Also refactor this commit: sweep: https://github.com/beetcb/ghdl/commit/1f17aa96e33c912de7557612df3e628d5f91ebaf