run-linters: avoid searching scripts in build/

During package build the Python code is copied to the `build` directory.
Ignore this directory when searching for Python scripts.

run-linters

@@ -4,7 +4,7 @@ set -eu
 # Copyright 2023, Canonical Ltd.
 # SPDX-License-Identifier: GPL-3.0
 
-PYTHON_SCRIPTS=$(grep -l -r '^#! */usr/bin/python3$' .)
+PYTHON_SCRIPTS=$(find . -maxdepth 1 -type f -exec grep -l '^#! */usr/bin/python3$' {} +)
 
 run_black() {
     echo "Running black..."