fix: Avoid inserting search_path again.

Author: linyihai

src/cargo/core/compiler/compilation.rs

@@ -323,7 +323,11 @@ impl<'gctx> Compilation<'gctx> {
 
         let dylib_path = paths::dylib_path();
         let dylib_path_is_empty = dylib_path.is_empty();
-        search_path.extend(dylib_path.into_iter());
+        if dylib_path.starts_with(&search_path) {
+            search_path = dylib_path;
+        } else {
+            search_path.extend(dylib_path.into_iter());
+        }
         if cfg!(target_os = "macos") && dylib_path_is_empty {
             // These are the defaults when DYLD_FALLBACK_LIBRARY_PATH isn't
             // set or set to an empty string. Since Cargo is explicitly setting

tests/testsuite/build.rs

@@ -2173,9 +2173,8 @@ fn issue_14194_deduplicate_library_path_env_var() {
                             let lib_path = std::env::var("{}").unwrap();
                             let paths: Vec<_> = std::env::split_paths(&lib_path).collect();
                             if paths.len() > 1 {{
-                                // The first path will be prepended to the search path in the next run
                                 let first = &paths[0];
-                                assert!(paths[1..].contains(&first));
+                                assert!(!paths[1..].contains(&first));
                             }}
                             return; 
                         }}