There are two variables that CMake takes into account during
find_package() in cross-compiled environments, which are: CMAKE_SYSROOT
and CMAKE_FIND_ROOT_PATH. Those are used in cmFindCommon::RerootPaths()
function, which blindly prepends all search paths with those specified
via CMAKE_SYSROOT and CMAKE_FIND_ROOT_PATH.
Extend search paths by using CMAKE_SYSROOT and CMAKE_FIND_ROOT_PATH in a
similar way as CMake does, so we successfully find CMake packages
information in cross-compiled environments.