Add support for the `x86_64-unknown-linux-musl` platform

[davidbtadokoro]

Description:

Rust offers two generic Linux targets: x86_64-unknown-linux-gnu and x86_64-unknown-linux-musl. In a nutshell, -x86_64-unknown-linux-gnu is more compatible with various Linux distributions due to its reliance on the widely used glibc. At the same time, x86_64-unknown-linux-musl produces more portable and self-contained binaries because it includes all necessary libraries within the binary itself.

How to reproduce:

I started trying to support -musl also, as it seemed really plug-n-play along with cargo dist, but encountered failing jobs [1], which seemed to be generated by a cross-compilation problem [2].

[1]: log of the failed job to build for the x86_64-unknown-linux-musl platform.
[2]: Thread reporting similar error shown in log.

Expected behavior:

If possible, we should make it as portable as possible for all Linux systems.