Make it possible to run heaptrack from the build folder

Make it possible to run heaptrack from the build folder

By setting the correct CMake properties, the libraries, shell runner
and executables land in the correct folder layout in the build
directory. This way, we can run heaptrack directly from the build
dir, i.e.:

cd heaptrack/build
make
./bin/heaptrack <your app>
./bin/heaptrack_gui <data file>