Compilation failure on DragonFlyBSD

[paragw]

error[E0432]: unresolved import libc::__error
--> /home/vmuser/.cargo/registry/src/github.com-1ecc6299db9ec823/getrandom-0.1.13/src/util_libc.rs:22:13
|
22 | use libc::__error as errno_location;
| ^^^^^^-------^^^^^^^^^^^^^^^^^^
| | |
| | help: a similar name exists in the module: ferror
| no __error in the root

error: aborting due to previous error

For more information about this error, try rustc --explain E0432.
error: Could not compile getrandom.

[josephlr]

I was able to reproduce this with cargo xbuild --target x86_64-unknown-dragonfly. For context, we attempted to get errno working correctly on DragonFlyBSD via rust-lang/libc#1432 but that only allows it to work when libc is a dep of libstd. The is because:

• DragonflyBSD (unlike every other UNIX target) uses a thread-local static variable directly for its errono (as opposed to going through a helper method like __error or _errno_locaiton.
• Rust thread-local statics are not stable, see Tracking issue for thread_local stabilization rust-lang/rust#29594

So we will probably just not bother with getting errno information on Dragonfly, which should fix the issue.