Skip test_aio_cancel_all on musl
Skip test_aio_cancel_all on musl

I suspect that the segfault is due to a stack overflow on musl's signal
stack, but I can't reproduce the failure locally.

Fixes #1169

asomers/nix,geofft/nix-rust,geofft/nix-rust,nix-rust/nix,geofft/nix-rust,asomers/nix,carllerche/nix-rust,carllerche/nix-rust,nix-rust/nix,carllerche/nix-rust