Two reliability defects that bit this session: a wedged suite could
hang the runner (and the single local build slot) forever, and the
mingw image failed to build on an arm64 Docker host because its i386
Wine packages are unsatisfiable.
- run-tests-parallel.sh now caps each suite with `timeout --kill-after`
(900s default, 3600s for the legitimately-slow incremental suite),
where `timeout` exists; a killed suite fails loudly instead of
blocking. Hosts without `timeout` run uncapped as before.
- Dockerfile.mingw makes Wine best-effort: the cross-COMPILE toolchain
builds on any arch, and only the .exe-execution step needs Wine, so a
Wine-unavailable host still gets a working compile check.
Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>