Better rake:clean and rake:clobber for macOS

[ashie]

On macOS, rake:clean or rake:clobber doesn't remove some old artifacts, it causes including unexpected old version's artifacts into the package.

[ashie]

Although we should use artifacts from CI, we don't yet have CI for Apple Silicon.

[github-actions]

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[ashie]

td-agent/.bundle/config should be removed, it's generated by this build system.
I experienced that using old one causes lacking most gems in built package.