Add the installation prefix of "serial" to CMAKE_PREFIX_PATH or set

To add the installation prefix of "serial" to the `CMAKE_PREFIX_PATH` environment variable, you can use the following command:

export CMAKE_PREFIX_PATH=/path/to/serial:$CMAKE_PREFIX_PATH

Replace `/path/to/serial` with the actual installation prefix of the "serial" library.

Alternatively, you can set the `CMAKE_PREFIX_PATH` variable in your CMakeLists.txt file. Add the following line at the beginning of your CMakeLists.txt:

set(CMAKE_PREFIX_PATH "/path/to/serial" ${CMAKE_PREFIX_PATH})

Make sure to replace `/path/to/serial` with the actual installation prefix of the "serial" library.

By setting the `CMAKE_PREFIX_PATH` variable, CMake will search for libraries and headers in the specified prefix path when building your project.