Optimizing shared libraries using profile driven optimizations?

Hello,

I would like to compile a dynamically loaded shared library using
profile driven optimizations.
I compiled and linked the lib with -fprofile-generate=..., but no
profile is beeing generated at runtime.

I can't compile the whole program with those optimizations, its a
really large beast with a compile and huge build system.

Any ideas how I could archieve this?

Thank you in advance, Clemens