test(build-std): regression test for rust-lang#16489

Author: weihanglo

tests/testsuite/mock-std/library/compiler_builtins/Cargo.toml

@@ -3,3 +3,4 @@ name = "compiler_builtins"
 version = "0.1.0"
 authors = ["Alex Crichton <[email protected]>"]
 edition = "2018"
+links = "compiler-rt"

tests/testsuite/mock-std/library/compiler_builtins/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("cargo:compiler-rt=foo");
+}

tests/testsuite/standard_lib.rs

@@ -866,3 +866,24 @@ fn fetch() {
         .with_stderr_does_not_contain("[DOWNLOADED] [..]")
         .run();
 }
+
+#[cargo_test(build_std_mock)]
+fn std_build_script_metadata_not_propagate_to_user() {
+    // See below for why we added this test:
+    // <https://github.com/rust-lang/cargo/pull/16489>
+    let setup = setup();
+
+    let p = project()
+        .file("src/lib.rs", "")
+        .file(
+            "build.rs",
+            r#"
+            fn main() {
+                assert!(std::env::var("DEP_COMPILER_RT_COMPILER_RT").is_err());
+            }
+            "#,
+        )
+        .build();
+
+    p.cargo("check").build_std(&setup).target_host().run();
+}