If only HSA is enabled we dont need pciutils since AMD detection does
not rely on it. Therefore we change CMakeLists.txt to build pciutils
only if required.
This commit has some side-effects:
1. We now don't build Intel backend by default. In other words, no
backend is built by default, the user must specify which backend
to use.
2. There were some issues with includes and wrongly used defines and
variables. This commit fixes all that.
