Validate the uniqueness of build scripts

Author: namanlp

src/cargo/util/toml/targets.rs

@@ -104,6 +104,7 @@ pub(super) fn to_targets(
         if metabuild.is_some() {
             anyhow::bail!("cannot specify both `metabuild` and `build`");
         }
+        validate_unique_build_scripts(custom_build)?;
         for script in custom_build {
             let script_path = Path::new(script);
             let name = format!(
@@ -901,6 +902,22 @@ fn validate_unique_names(targets: &[TomlTarget], target_kind: &str) -> CargoResu
     Ok(())
 }
 
+/// Will check a list of build scripts, and make sure script file stems are unique within a vector.
+fn validate_unique_build_scripts(scripts: &[String]) -> CargoResult<()> {
+    let mut seen = HashSet::new();
+    for script in scripts {
+        let stem = Path::new(script).file_stem().unwrap().to_str().unwrap();
+        if !seen.insert(stem) {
+            anyhow::bail!(
+                "found duplicate build script file stem {}, \
+                but all build scripts must have a unique file stem",
+                stem
+            );
+        }
+    }
+    Ok(())
+}
+
 fn configure(
     toml: &TomlTarget,
     target: &mut Target,