LIBPATH is used as dylib's path environment variable on AIX

src/bootstrap/dylib_util.rs

@@ -12,6 +12,8 @@ pub fn dylib_path_var() -> &'static str {
         "DYLD_LIBRARY_PATH"
     } else if cfg!(target_os = "haiku") {
         "LIBRARY_PATH"
+    } else if cfg!(target_os = "aix") {
+        "LIBPATH"
     } else {
         "LD_LIBRARY_PATH"
     }