The intent of the previous implementation was to avoid libc, but it turns out that just invoking a syscall without libc is complicated (see https://github.com/docker-library/hello-world/pull/62#issuecomment-568573535 for details).
On the other hand, my personal machine can cross-compile all of musl in ~30s per architecture, which is pretty reasonable, and the resulting binary sizes are only around ~10k each, and I was able to do so successfully for every architecture we currently support.
```console
$ ./amd64/hello-world/hello
Hello from Docker!
This message shows that your installation appears to be working correctly.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
To try something more ambitious, you can run an Ubuntu container with:
$ docker run -it ubuntu bash
Share images, automate workflows, and more with a free Docker ID:
https://cloud.docker.com/
For more examples and ideas, visit:
https://docs.docker.com/engine/userguide/
```
Build a minimal version in C instead of assembly so it easily can be
ported to other archs.
This statically linked C version builds a binary that is 1472 bytes.
fixes#7
Nikolay Korolev