message: build_system: fix clean task in Makefile
diff: @@ -164,7 +164,7 @@ distclean:
  @rm -rf logs/
  clean:
  - @if [ -d build ]; then find build -mindepth 2 -path build/*/external -prune -o -exec rm -rf {} +; fi
  + @if [ -d build ]; then find build -mindepth 2 -path "build/*/external" -prune -o -exec rm -rf {} +; fi
  android_env_check:
  ifndef ANDROID_TOOLCHAIN_CMAKE
  