feat(ci): add CI check for EXTRA_COMPONENT_DIRS in examples

tools/ci/check_examples_extra_component_dirs.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+set -uo pipefail
+
+# Examples shouldn't use EXTRA_COMPONENT_DIRS, instead the dependencies should be specified in idf_component.yml files
+
+output=$(find ${IDF_PATH}/examples -name "CMakeLists.txt" -not -path "**/managed_components/**" -not -path "**/build/**")
+files=$(egrep "set\(EXTRA_COMPONENT_DIRS" ${output} | cut -d ":" -f 1)
+found_issues=0
+for file in ${files}
+do
+    if [ "$file" == "${IDF_PATH}/examples/system/unit_test/test/CMakeLists.txt" ]; then
+        # this specific one is okay
+        continue
+    fi
+    echo "${file} uses EXTRA_COMPONENT_DIRS. Change it to reference the component using idf_component.yml file."
+    ((found_issues++))
+done
+
+if [ $found_issues -eq 0 ]; then
+    echo "No examples use EXTRA_COMPONENT_DIRS"
+    exit 0
+fi
+
+exit 1