UART 16550 under x86_64 interrupts cause triple fault on baremetal under x86_64

[Qix-]

Serial communication works as expected under baremetal as long as the UART's external interrupts are not enabled.

I currently suspect this was found out when connecting a sort of turnkey serial debugger to the machine and it was sending back something on the mobo's RX line, causing a data interrupt to be fired - but early on in the execution of things, a proper IDT is not set up (even a temporary one). One should absolutely be set up (even the "main" kernel's IDT is not very fleshed out) but the workaround for the moment is to simply disable debug logging on baremetal.