cfg!(test) doesn't seem to work for build.rs

[azerupi]

When using a build.rs file, cargo doesn't seem to pass the test flag when cargo test is used.

fn main() {
    if cfg!(test) { ... }
}

Does not work. As a workaround you can use features:

fn main() {
    if cfg!(feature="test") { ... }
}

But it requires you to use cargo test --features=test

[alexcrichton]

Yeah today build scripts aren't re-run for tests (only for libraries), but I think this is covered by #1581 so closing in favor of that. Thanks for the report though!