Beforehand:
```text
❯ env CARGO_LOG=cargo::core::compiler::fingerprint=info cargo test -p query_tests
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] stale: changed "/home/mneumann/src/influxdb_iox/query_tests/cases"
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] (vs) "/home/mneumann/src/influxdb_iox/target/debug/build/query_tests-0e8f741dfb84437f/output"
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] FileTime { seconds: 1625474716, nanos: 436081357 } != FileTime { seconds: 1625474752, nanos: 52625167 }
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] fingerprint error for query_tests v0.1.0 (/home/mneumann/src/influxdb_iox/query_tests)/Test/TargetInner { ..: lib_target("query_tests", ["lib"], "/home/mneumann/src/influxdb_iox/query_tests/src/lib.rs", Edition2018) }
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] err: current filesystem status shows we're outdated
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] fingerprint error for query_tests v0.1.0 (/home/mneumann/src/influxdb_iox/query_tests)/RunCustomBuild/TargetInner { ..: custom_build_target("build-script-build", "/home/mneumann/src/influxdb_iox/query_tests/build.rs", Edition2018) }
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] err: current filesystem status shows we're outdated
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] fingerprint error for query_tests v0.1.0 (/home/mneumann/src/influxdb_iox/query_tests)/Build/TargetInner { ..: lib_target("query_tests", ["lib"], "/home/mneumann/src/influxdb_iox/query_tests/src/lib.rs", Edition2018) }
[2021-07-05T08:52:13Z INFO cargo::core::compiler::fingerprint] err: current filesystem status shows we're outdated
Compiling query_tests v0.1.0 (/home/mneumann/src/influxdb_iox/query_tests)
```
The issue is that both the input and the test output files are located
under `cases/`. `build.rs` used `cargo:rerun-if-changed=cases` which per
Cargo doc will scan ALL files in that directory. Note that the normal
`exclude` directive in `Cargo.toml` does NOT work, see
https://github.com/rust-lang/cargo/issues/4587 .
So we need to split input and output files into separate directories
(`cases/{in,out}`).
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