patch 9.1.0459: Vim9: import autoload does not work with symlink

Problem:  Vim9: import autoload does not work with symlink
          (Olivier Dormond)
Solution: set sn_autoload_prefix in check_script_symlink
          (nwounkn)

fixes: #14775
closes: #14885

Signed-off-by: nwounkn <nwounkn@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/scriptfile.c b/src/scriptfile.c
index b6c66b7..6a6a037 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -435,8 +435,13 @@
 	    si = SCRIPT_ITEM(sid);
 	    si->sn_sourced_sid = real_sid;
 	    if (new_sid)
+	    {
 		SCRIPT_ITEM(real_sid)->sn_import_autoload
 						    = si->sn_import_autoload;
+		if (si->sn_autoload_prefix != NULL)
+			SCRIPT_ITEM(real_sid)->sn_autoload_prefix =
+				vim_strsave(si->sn_autoload_prefix);
+	    }
 	}
     }
     vim_free(real_fname);