aseba-test-natives-count linking error on Linux

Created by: FabianHahn

The commit message for 337e7c5e states:

• [...]
• Fix dynamic link error when building aseba-test-natives-count
• [...]

However, as far as I can see it, all the components for these unit tests are statically linked, including asebavm and asebadummycallbacks. The problem is that there exists a circular dependency between those two libraries, which results in the following Linking error on current Debian testing, using GCC (Debian 5.2.1-17) and CMake 3.3.2:

[ 97%] Linking CXX executable aseba-test-natives-count
cd /home/fabian/Projects/aseba/build/tests && /usr/bin/cmake -E cmake_link_script CMakeFiles/aseba-test-natives-count.dir/link.txt --verbose=1
/usr/bin/c++   -g   CMakeFiles/aseba-test-natives-count.dir/aseba-test-natives-count.cpp.o  -o aseba-test-natives-count -rdynamic ../compiler/libasebacompiler.a ../vm/libasebavm.a libasebavmdummycallbacks.a ../transport/dashel_plugins/libasebadashelplugins.a ../common/libasebacommon.a /home/fabian/Projects/dashel/build/libdashel.a -ludev
libasebavmdummycallbacks.a(asebavmdummycallbacks.cpp.o): In function `AsebaAssert':
/home/fabian/Projects/aseba/tests/asebavmdummycallbacks.cpp:120: undefined reference to `AsebaVMInit'
collect2: error: ld returned 1 exit status
tests/CMakeFiles/aseba-test-natives-count.dir/build.make:101: recipe for target 'tests/aseba-test-natives-count' failed

The proposed commit fixes this linking issue by reverting the respective change to tests/CMakeLists.txt from 337e7c5e, but since I do not know the reason for the original change, I cannot tell whether there will be any side effects on other build environments.