This was requested by a forum user, and I thought why not.
It's a simple change to make since DiscIO already supports it,
and I assume command-line users know roughly what they're doing.
New dolphin-tool command: "header"
-b / --block_size
-c / --compression
-l / --compression_level
Informative RVZ/WIA header2 value "compression_level" is now a s32 instead of a u32, because negative compression is a thing.
Speaking of, it is now possible to use negative compression levels in dolphin-tool's convert command (not the GUI, though).
DiscIO depends on some IOS functions and other functions, which are in Core and not Common. This results in link errors if using DiscIO on its own (which is why DolphinTool had a listed dependency on videocommon; videocommon has a dependency on core so adding that made things build).
Videocommon also depends on core, which resulted in linking errors (though I'm not sure why). Ideally, dolphintool woudln't depend on videocommon... but some stuff in core does.