Make gdbclient.py work in directories other than the root.

Change-Id: I8e383052e15f41919c7107bf960092120d2c621c
diff --git a/scripts/gdbclient.py b/scripts/gdbclient.py
index 4b7de2d..df924eb 100755
--- a/scripts/gdbclient.py
+++ b/scripts/gdbclient.py
@@ -65,7 +65,7 @@
                  "{}/build/core/config.mk".format(root),
                  "dumpvar-{}".format(variable)]
 
-    make_output = subprocess.check_output(make_args)
+    make_output = subprocess.check_output(make_args, cwd=root)
     return make_output.splitlines()[0]