add musl support

[developer-guy]

For Linux, you probably want musl (e.g. x86_64-linux-musl) because your resulting binary will be statically linked and thus work on all Linux distributions. However, if you prefer to interact with the system glibc, such as on Ubuntu, you can specify gnu (e.g. x86_64-linux-gnu).

[dosgo]

ou can manually set the environment variable ZIGTARGET using musl.