Cannot compile for musl because of missing libc::NFS_SUPER_MAGIC

[jirutka]

libc crate does not provide NFS_SUPER_MAGIC for musl libc (don’t know why). This constant is used in cargo/util/flock:295.

[alexcrichton]

I'd be fine with either just not executing this check on musl or hardcoding the value of NFS_SUPER_MAGIC, it looks like musl doesn't have a definition for that in its header files.

[jirutka]

To be honest, I have no clue what implications it may have when you hard-code that value, so the decision is up to you. I’ve simply disabled that check in Alpine package for cargo.

[alexcrichton]

Yeah that's fine, do you want to upstream that as well? I'd be more than fine taking a PR for that!