Suggestion for third party libraries

Hi ThinLTO experts,
Majority of our code base is using something like bazel as build system.
However, for third party libraries, because they don’t natively support bazel, we are prebuilding those libraries and linking them with the main binary.
This becomes an issue for thinlto build, because those prebuilt libraries cannot participate in thin link step of the binary like normal source code, and also don’t have its own thin backend.
Do you have any suggestion for how to handle those third party libraries, so that it can be fully optimized with pgo+thinlto?