Replace INCLUDE(FindPkgConfig) by FIND_PACKAGE(PkgConfig REQUIRED)
to avoid following warning:
warning: The package name passed to `find_package_handle_standard_args` (PkgConfig) does not match the name of the calling package (SKIQ). This can lead to problems in calling code that expects `find_package` result variables (e.g., `_FOUND`) to follow a certain pattern.