ci: don't run build system tests on unit_test or custom_test labels

tools/ci/config/build.yml

@@ -272,6 +272,12 @@ build_docs_zh_CN_esp32s2:
 
 test_build_system:
   extends: .build_template
+  only:
+    variables:
+      - $BOT_TRIGGER_WITH_LABEL == null
+      - $BOT_LABEL_BUILD
+      - $BOT_LABEL_REGULAR_TEST
+      - $BOT_LABEL_WEEKEND_TEST
   script:
     - ${IDF_PATH}/tools/ci/test_configure_ci_environment.sh
     - rm -rf test_build_system
@@ -281,6 +287,12 @@ test_build_system:
 
 test_build_system_cmake:
   extends: .build_template
+  only:
+    variables:
+      - $BOT_TRIGGER_WITH_LABEL == null
+      - $BOT_LABEL_BUILD
+      - $BOT_LABEL_REGULAR_TEST
+      - $BOT_LABEL_WEEKEND_TEST
   script:
     - ${IDF_PATH}/tools/ci/test_configure_ci_environment.sh
     - rm -rf test_build_system