External libraries, fetched by fetch_externals.sh / .cmd (git-ignored).
Our CMake wrappers for them live in cmake/<lib>/ (tracked in git).

residfp-2011 is a second clone of the libsidplayfp mirror, at tag 0.1.1: Antti Lankila's
original resid-fp, the Lankila engine (cmake/residfp-2011/).

libusb is at v1.0.30 and built by our own wrapper (cmake/libusb/), not by its autotools,
Xcode or MSBuild projects: static, logging off, with one hand-written config.h for all
platforms (cmake/libusb/generated/). It is LGPL-2.1-or-later, for USB SID devices.

libarchive (v3.8.9, BSD-2-Clause) and xz (v5.8.4, for liblzma, 0BSD) unpack HVSC's 7z
releases (cmake/libarchive/, cmake/xz/). Both are built by their own CMake with everything
optional off; only libarchive's 7z reader is used, and the linker drops the rest. Their
mirrors are extlib/libarchive and extlib/tukaani-project-xz (branches and tags pushed from
github.com on 2026-10-11).
