error with exported yaml library

edit

I am cross-compiling ROS2 dashing onto a FreeBSD-based system. I have a CrossToolchain.cmake file which seems to be working just fine.

When I'm building everything in my workspace, I get the following error:

--- stderr: rcl_yaml_param_parser
CMake Warning at /home/broomstick/cheri/ros2_dashing_min/install/libyaml_vendor/share/libyaml_vendor/cmake/ament_cmake_export_libraries-extras.cmake:116 (message):
  Package 'libyaml_vendor' exports library 'yaml' which couldn't be found
Call Stack (most recent call first):
  /home/broomstick/cheri/ros2_dashing_min/install/libyaml_vendor/share/libyaml_vendor/cmake/libyaml_vendorConfig.cmake:38 (include)
  CMakeLists.txt:8 (find_package)
---

libyaml_vendor itself seems to build just fine, and libyaml.so ends up in <prefix>/install/libyaml_vendor/lib, which seems reasonable.

Also, my application seem to run just fine, despite this error, but I assume that's because all my applications are small demos that don't use the functionality. All the same, I'd like to understand and fix it.

I suspect this has something to do with my CrossToolchain.cmake file and CMAKE_PREFIX_PATH (which points into my sysroot), but I'm not sure. For other <package>_vendor packages, like poco, I've actually built the library separately and ensure its cmake files are on my CMAKE_PREFIX_PATH, but yaml_vendor doesn't seem to provide an option (i.e., it doesn't look for an existing library first before downloading and building it locally).

Any help would be appreciated.