Moved FFT library processing to separate module

Helps make the main CMakeLists.txt more readable.

Change-Id: Ia846863edb4471c9c85480d82b5c5cce4225b074
Moved shared/static library detection to separate module

Helps make the main CMakeLists.txt more readable.

Change-Id: Iaf1c3734ceeaf36a532be424c7429931534844d5