This image can be also found in GHCR and Quay.io.
Dockerfile can be found at abcfy2/docker-mingw-cross-toolchain-ubuntu#Dockerfile.
This is the musl based toolchain from mingw-cross.
This is useful for some building environments which require a glibc based library.
Cross toolchain installed in /cross_root. And /cross_root/bin has been already appended to PATH, so you can use cross compiler like arm-linux-unknown-musleabi-gcc -v directly.
An useful example can be found at abcfy2/aria2-static-build