[llvm] [llvm-cgdata] Remove GENERATE_DRIVER option (PR #100077)

[Nico Weber via llvm-commits]

nico wrote:

@MaskRay might know if `Opt` has built-in subcommand support.

IIRC there were RFCs about moving from cl:: to `Opt` and there was general support. @MaskRay probably knows more about that too :)

https://github.com/llvm/llvm-project/pull/100077