Add option for CLI arg -d

[Ebola16]

Recently I have found several bugs in Dolphin's debugger. https://bugs.dolphin-emu.org/issues/10594 is an example.

If DBT could start builds with -d, that'd make bisecting a lot easier.

[Helios747]

Solid recommendation. That could be pretty useful.

I think the debugger is the only useful CLI arg worth supporting, but do you see any value in going through the extra effort to support arbitrary CLI args that the user enters and leaving it up to them to get right?

[Ebola16]

If -d is the only argument that has otherwise inaccessible features on a release build then I'm fine with only supporting that one.