Errors During QT program compilation in Linux: qmakespec has not been set, so configuration cannot be deduced.

This is because, in the new machine environment, you want to change the installation directory of QT, from the original directory A to directory B, without re-compiling QT Source code, But compiled ProgramAnd the library directly to the new directory, set the qtdir environment variable to the new directory. However, the above error is found. The reason is that CodeThe configured directory is the original directory. Therefore, when using dynamic libraries and programs, you can find the directory according to the original configuration. All pri files are compiled as the configured directory. This causes the above problems. The solution is to configure and recompile QT according to the changed directory.