Add baseline feature to help rackscale benches take less time.

Author: hunhoffe

doc/src/benchmarking/Baselines.md

@@ -69,3 +69,7 @@ Run:
 ```bash
 CXX=g++-4.8 CC=gcc-4.8 make qemu`
 ```
+
+# Rackscale
+
+One of the baselines for rackscale is NrOS. To run the rackscale benchmarks with corresponding NrOS baslines, run them with ```--feature baseline```.

kernel/Cargo.toml

@@ -111,6 +111,8 @@ gdb = []
 integration-test = ["shmem", "ethernet"]
 # smoke: Shortens long running benchmarks to test just functionality.
 smoke = []
+# For rackscale tests, runs baseline NrOS. This causes the tests to take longer.
+baseline = []
 # baremetal: Compile benchmarks for running on bare-metal.
 baremetal = []
 # pre-alloc guest memory: For benchmark sensitive to VM exits.