Add testcase if nightly not enabled for multiple build scripts

Author: namanlp

tests/testsuite/build_scripts_multiple.rs

@@ -0,0 +1,31 @@
+//! Tests for multiple build scripts feature.
+
+use cargo_test_support::prelude::*;
+use cargo_test_support::project;
+use cargo_test_support::str;
+
+#[cargo_test]
+fn build_without_nightly_aborts_with_error() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                edition = "2024"
+                build = ["build1.rs"]
+            "#,
+        )
+        .build();
+    p.cargo("check")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[ERROR] failed to parse manifest at `[ROOT]/foo/Cargo.toml`
+
+Caused by:
+  `build = […]` requires `-Z multiple-build-scripts`
+
+"#]])
+        .run();
+}

tests/testsuite/main.rs

@@ -16,6 +16,7 @@ mod build_plan;
 mod build_script;
 mod build_script_env;
 mod build_script_extra_link_arg;
+mod build_scripts_multiple;
 mod cache_lock;
 mod cache_messages;
 mod cargo;