Bazel CI: rules_rust is failing on darwin

[meteorcloudy]

https://ci.bazel.build/blue/organizations/jenkins/rules_rust/detail/rules_rust/800/pipeline

suspect: 2a3f859
@davidzchen Can you take a look?

running 1 test
test test::test_can_read_data_from_runfiles ... FAILED
failures:
---- test::test_can_read_data_from_runfiles stdout ----
thread 'test::test_can_read_data_from_runfiles' panicked at 'called `Result::unwrap()` on an `Err` value: Error { repr: Os { code: 2, message: "No such file or directory" } }', src/libcore/result.rs:860:4
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failures:
test::test_can_read_data_from_runfiles
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

[acmcarther]

#66 fixes this, waiting on review from another maintainer.

[acmcarther]

Was fixed with #66