multiarch/qemu-user-static stopped at QEMU 7.2 (January 2023). Under it,
qmake's compiler probe (`g++ -E -v` in toolchain.prf) returns nothing on the
current gcc 16 toolchain, so every qmake package fails on aarch64 with
"failed to parse default include paths from compiler output" (hype, PR #517).
The same PKGBUILD builds under QEMU 10.2.3 and 11.1.
Register through tonistiigi/binfmt at a pinned tag, on both the ephemeral
builder droplets and the rootful-Docker path of setup_qemu, uninstalling any
existing entry first because the tool keeps an older registration in place.
The tag is now the one place that decides what every emulated build runs
under. Flags stay F and C, which rootless sudo inside the builder needs.
Ryan Hughes
efff828746