Cannot compile cupi in my project - transitive dependency problems?

[andrewjensen]

I'm trying to compile the blink example project on my Raspberry Pi Zero W, but the build command fails as it tries to compile cupi. I'm getting this terminal output:

$ cargo build --verbose
       Fresh byteorder v1.2.1
       Fresh libc v0.2.39
       Fresh winapi-build v0.1.1
       Fresh cfg-if v0.1.2
       Fresh bitflags v0.3.3
       Fresh bitflags v0.4.0
       Fresh winapi v0.2.8
       Fresh libc v0.1.12
       Fresh semver v0.1.20
       Fresh void v1.0.2
       Fresh bitflags v1.0.1
       Fresh iovec v0.1.2
       Fresh rand v0.4.2
       Fresh rustc_version v0.1.7
       Fresh bytes v0.4.6
       Fresh nix v0.10.0
       Fresh kernel32-sys v0.2.2
       Fresh remove_dir_all v0.3.0
       Fresh nix v0.6.0
       Fresh tempdir v0.3.6
       Fresh spidev v0.3.0
       Fresh mmap v0.1.1
   Compiling cupi v0.1.0
     Running `rustc --crate-name cupi /home/pi/.cargo/registry/src/github.com-1ecc6299db9ec823/cupi-0.1.0/src/lib.rs --crate-type lib --emit=dep-info,link -C debuginfo=2 -C metadata=409ed042e1991471 -C extra-filename=-409ed042e1991471 --out-dir /home/pi/cupi-test/target/debug/deps -L dependency=/home/pi/cupi-test/target/debug/deps --extern spidev=/home/pi/cupi-test/target/debug/deps/libspidev-a197c99928c90dc7.rlib --extern bitflags=/home/pi/cupi-test/target/debug/deps/libbitflags-b4df5465fcb6918f.rlib --extern libc=/home/pi/cupi-test/target/debug/deps/liblibc-d67d33f8bf527dba.rlib --extern mmap=/home/pi/cupi-test/target/debug/deps/libmmap-492832427199866f.rlib --extern nix=/home/pi/cupi-test/target/debug/deps/libnix-f1ec6b05c8d84a61.rlib --cap-lints allow`
error[E0432]: unresolved import `nix::sys::ioctl::libc`
  --> /home/pi/.cargo/registry/src/github.com-1ecc6299db9ec823/cupi-0.1.0/src/lib.rs:62:22
   |
62 | use nix::sys::ioctl::libc::geteuid;
   |                      ^^^^ Could not find `libc` in `ioctl`

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0432"
error: Could not compile `cupi`.

I'm still very much a Rust noob, so does this mean I'm having problems with dependency versions within nix, libc, and ioctl? Should I try to pin one of these versions in my lockfile, or is there something else I should try?

Thanks!