fix gdb libtool invocation path
diff --git a/tests/runtests.pl b/tests/runtests.pl
index b1bb558..8b2ec5a 100755
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -4933,7 +4933,7 @@
     if($c eq "#! /") {
         # A shell script. This is typically when built with libtool,
         $libtool = 1;
-        $gdb = "libtool --mode=execute gdb";
+        $gdb = "../libtool --mode=execute gdb";
     }
 }