Ubuntu 20.04 and 22.04 both have the same FFmpeg versions, but FFmpeg on
20.04 was built with version 9 of NVENC headers, whereas 22.04 was built
with 11.
Unfortunately, that means we have to revert back to the old presets when
Ubuntu 20.04 is detected. The way this detection is done is a bit hacky,
but it's the only way to preserve startup performance. Otherwise we'd
have to write yet another startup subprocess test program to detect
whether the FFmpeg being used was built with older or newer NVENC, which
is both slow to start up and annoying to write. So instead, just get the
distro name/version strings and detect Ubuntu 20.04 that way.
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