DEP_* env variable not set in nightly test run

[kamulos]

This happens with the nightly version, but not with the stable.

> cargo +nightly version
cargo 1.51.0-nightly (329895f5b 2021-01-06)

Reproduce

Cargo.toml

[package]
name = "asdf"
version = "0.1.0"
authors = ["xyxy"]
edition = "2018"

[dependencies]
libsodium-sys = "0.2"

[build-dependencies]
cc = "1.0"

test.c

void test() {}

build.rs

fn main() {
    cc::Build::new()
        .file("test.c")
        .include(std::env::var_os("DEP_SODIUM_INCLUDE").expect("DEP_SODIUM_INCLUDE is not set"))
        .compile("test.a");
}

Now just run cargo +nighly test. With stable this works perfectly, with nightly the DEP_SODIUM_INCLUDE env variable is not set.

[ehuss]

@alexcrichton I think this was caused by #8969. When running cargo test, the test unit has a dependency edge to the local build script. Since tests got disconnected, that causes the build script to start building too early (before the libsodium-sys build script runs).

[alexcrichton]

Thanks for the report! I think this should be fixed by #9065. Sorry about the breakage!

[rylev]

FYI: This caused only one breakage in the latest crater run.