Build benchmarks instead of adding binaries

[multics69]

Instead of adding benchmark binaries, it is better to include the benchmark source code (git subtree?) and build them from the top makefile. This way, we can remove the version dependencies between benchmark binaries and Linux distros. But it is not an urgent task.

./userspace
├── bench_bin
│   ├── btree_mt
│   ├── graph500
│   └── XSBench