Fix env/cfg set for `cargo test` and `cargo run`.#9122

Merged

bors merged 2 commits intorust-lang:masterfrom

ehuss:fix-multiple-run-custom-build

Feb 3, 2021

Commits on Feb 2, 2021

Fix env/cfg set for `cargo test` and `cargo run`.
ehuss
committed

Commits on Feb 3, 2021

Add note about `cargo:rustc-env` variables set at runtime.
ehuss
committed