clippy_failure_test is silently failing

CI is green, but the test is actually failing. [Example](https://buildkite.com/bazel/rules-rust-rustlang/builds/6723#0181d878-dff6-40a4-8e69-3b2039df41ba) (this is from the first failing commit):

> Testing bad_test_clippy... stat: cannot stat '/tmp/ci-vr9W8fqJ3x/rules_rust_test_clippy/bazel-bin/test/clippy/bad_test.clippy.out': No such file or directory

It started failing in https://github.com/bazelbuild/rules_rust/pull/1434, because that PR resulted in the `bad_test.clippy.out` file moving into a subdirectory.

[Here](https://buildkite.com/bazel/rules-rust-rustlang/builds/6713#0181d3d2-08b8-444a-ad5b-eaa10c2d8ee1) is the build from the prior commit, where the test is passing.