Build aarch64 musl wheel on GitHub Action

[messense]

You can try the aarch64 wheel built in https://github.com/messense/maturin/actions/runs/573701516,
download link: https://github.com/messense/maturin/suites/2056522682/artifacts/41476397

Inspired by py-spy: https://github.com/benfred/py-spy/blob/master/.github/workflows/build.yml

[messense]

Tested on python:3.9 docker container.

root@390a38d3babc:/io# pip install maturin-0.9.1-py3-none-manylinux2014_aarch64.whl
Processing ./maturin-0.9.1-py3-none-manylinux2014_aarch64.whl
Requirement already satisfied: toml~=0.10.0 in /usr/local/lib/python3.9/site-packages (from maturin==0.9.1) (0.10.2)
Installing collected packages: maturin
Successfully installed maturin-0.9.1
root@390a38d3babc:/io# maturin --help
maturin 0.9.1
Build and publish crates with pyo3, rust-cpython and cffi bindings as well as rust binaries as python packages

USAGE:
    maturin <SUBCOMMAND>

FLAGS:
    -h, --help
            Prints help information

    -V, --version
            Prints version information


SUBCOMMANDS:
    build          Build the crate into python packages
    develop        Installs the crate as module in the current virtualenv
    help           Prints this message or the help of the given subcommand(s)
    list-python    Searches and lists the available python installations
    publish        Build and publish the crate as python packages to pypi
    sdist          Build only a source distribution (sdist) without compiling
root@390a38d3babc:/io# file `which maturin`
/usr/local/bin/maturin: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, with debug_info, not stripped
root@390a38d3babc:/io# uname -a
Linux 390a38d3babc 4.19.121-linuxkit #1 SMP PREEMPT Thu Jan 21 15:45:22 UTC 2021 aarch64 GNU/Linux

[konstin]

Thank you, this finally removes all the drone ci problems 🎉