Fix building aseba-test-natives-count against static asebavm.
Created by: brettle
The essence of the problem is that there is a circular dependency between asebavm and asebavmdummycallbacks, and they need to be linked into aseba-test-natives-count differently depending on whether asebavm is built as a shared lib (which it is when building RPMS but not when building packages for Ubuntu/Debian). This pull request fixes the problem by just using an "if (BUILD_SHARED_LIBS)" in the CMakeLists.txt file to control the 2 different cases.
NOTE: I don't have an Ubuntu/Debian system to test on. Someone else needs to confirm that this works there.