arti git head (a11d2929) does not build on NetBSD

I see the following build problem:

   Compiling arti-client v0.6.0 (/disk/6/archive/foreign/arti/crates/arti-client)
error[E0425]: cannot find function `getresuid` in crate `libc`
   --> crates/arti-client/src/util.rs:56:31
    |
56  |                 let _ = libc::getresuid(&mut resuid[0], &mut resuid[1], &mut resuid[2]);
    |                               ^^^^^^^^^ help: a function with a similar name exists: `geteuid`
    |
   ::: /home/wiz/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.132/src/unix/mod.rs:871:5
    |
871 |     pub fn geteuid() -> uid_t;
    |     -------------------------- similarly named function `geteuid` defined here

error[E0425]: cannot find function `getresgid` in crate `libc`
   --> crates/arti-client/src/util.rs:57:31
    |
57  |                 let _ = libc::getresgid(&mut resgid[0], &mut resgid[1], &mut resgid[2]);
    |                               ^^^^^^^^^ help: a function with a similar name exists: `getegid`
    |
   ::: /home/wiz/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.132/src/unix/mod.rs:870:5
    |
870 |     pub fn getegid() -> gid_t;
    |     -------------------------- similarly named function `getegid` defined here

For more information about this error, try `rustc --explain E0425`.
error: could not compile `arti-client` due to 2 previous errors