[libc] Fix vendor implemented math functions not being exported (#65510)

Summary:
A previous introduced a new object type for the GPU functions
implemented by an external vendor library. This was done so they we did
not attempt to run tests on functions which we did not implement,
however this accidentally stopped them from being included in the actual
output. Fix this by checking the new type as well.

The long term goal is to remove this vendor handling altogether, but is
being used as a short-term solution to provide a math library on the
GPU which currently lacks one.