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.
A C compiler would very much be unable to build this code anyway.
Fixes https://bugs.dolphin-emu.org/issues/12096.
Replaces the inflexible INI functions in NativeLibrary.