add cli argument to set the license archive path

[jls5177]

Added "--license_db" argument to override the default archive path
set in the "github.com/google/licenseclassifier" module.

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[Bobgy]

With go1.16 embed feature, the license db is now included in the binary. Is there still a need to override the license archive?

I'm closing because this is staling, feel free to discuss further