fix(ci): skip redundant pip install in layer publishing

Author: ericdog

ci/input_files/build.yaml.tpl

@@ -198,6 +198,7 @@ publish-layer-{{ $environment_name }} ({{ $runtime.name }}-{{ $runtime.arch }}):
         {{- end}}
   before_script:
     - *install-python-tools
+    - export SKIP_PIP_INSTALL=true
     - EXTERNAL_ID_NAME={{ $environment.external_id }} ROLE_TO_ASSUME={{ $environment.role_to_assume }} AWS_ACCOUNT={{ $environment.account }} source ./ci/get_secrets.sh
   script:
     - STAGE={{ $environment_name }} PYTHON_VERSION={{ $runtime.python_version }} ARCH={{ $runtime.arch }} DOTENV={{ $dotenv }} ./ci/publish_layers.sh