tweak: be tolerant of missing newlines at EOF

[Laikulo]

This adds a final pass through virtual_sdcard's line pumper to avoid losing the last block of a file if it is unterminated.

[Laikulo]

(had a minor fight with the linter)

[pedrolamas]

Unless I'm mistaken, this seems to be the same as #6565, you might want to take a look to understand the reasoning behind the current behaviour.

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