SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

Continues the migration to using fmt.

Notably, this allows safely converting a map within USBUtils over to
containing string view instances, rather than std::string instances, as
fmt safely handles the formatting of string views.

CMake: Only link in Bochs on x86 platforms