1. 详细错误信息

　　/home/jello/openwrt/build_dir/target-aarch64_generic_gibc/fstools-2018-01-02-11efbf3b/libfstools/overlay.c: At top level:　　

　　cc1: error: unrecognized command line option '-Wno-format-truncation' [-Werror]

　　cc1: all warnings being treated as errors

　　CMakeFiles/fstools.dir/build.make:110: recipe for target 'CMakeFiles/fstools.dir/libfstools/overlay.c.' failed

　　make[6]: *** [CMakeFiles/fstools.dir/libfstools/overlay.c.o] Error 1

2. 解决办法

　　进入fstools源码中将CMakeLists.txt中的-Werror和-Wno-format-truncation都删掉即可

　　cd build_dir/target-aarch64_generic_gibc/fstools-2018-01-02-11efbf3b

　　vi CMakelist.txt (删掉-Werror和-Wno-format-truncation)