Qt:warning: The build directory is not at the same level as the source directory

-1: warning: The build directory is not at the same level as the source directory, which could be the reason for the build failure.

在Qt重新打开一个项目时，各种报错，最后一个提示如上。
参考了https://blog.csdn.net/neuq_jtxw007/article/details/78774324
左侧工具栏，点击：项目 - Build，发现了如下图的提示，更改构建目录到当前这个项目的源码同一级，问题解决。