The code you provided is not a complete code snippet...

The code you provided is not a complete code snippet but refers to a CMake command: pkg_check_modules. This command is a part of the FindPkgConfig module and is used to check for the existence of specified modules using the pkg-config tool.

The Unknown CMake command "pkg_check_modules" error typically occurs when the FindPkgConfig module has not been included in the CMakeLists.txt file. To resolve this error, ensure that you include the following line before using the pkg_check_modules command in your CMakeLists.txt:

find_package(PkgConfig REQUIRED)

This line tells CMake to find and load the necessary settings for the FindPkgConfig module, making the pkg_check_modules command available for use.