想问一下，这种错误是什么原因？
make[3]: *** [screenshot] 错误 1
make[3]:正在离开目录 `/home/tianchunlong/src/qt-embedded-linux-opensource-src-4.5.0-arm/examples/desktop/screenshot'
make[2]: *** [sub-screenshot-make_default-ordered] 错误 2
make[2]:正在离开目录 `/home/tianchunlong/src/qt-embedded-linux-opensource-src-4.5.0-arm/examples/desktop'
make[1]: *** [sub-desktop-make_default] 错误 2
make[1]:正在离开目录 `/home/tianchunlong/src/qt-embedded-linux-opensource-src-4.5.0-arm/examples'
make: *** [sub-examples-make_default-ordered] 错误 2
