[llvm] r206228 - [ARM64][MC] Set the default CPU string to generic.

[Tim Northover]

> No, I'm saying that the default CPU in the JIT should always be the CPU
> we're actually running on.  That's not insane, that's how any sensible JIT
> would work.

Possibly (though the lldb developers may quibble about their JIT not
being sensible). That wasn't the behaviour before though, it just
randomly picked Cyclone for the giggles.

Tim.