[C++] Set CPU affinity

Sticking to a single processor improves the performance while
we are running only a single thread.
diff --git a/Makefile.ckati b/Makefile.ckati
index cf5bab8..38e1feb 100644
--- a/Makefile.ckati
+++ b/Makefile.ckati
@@ -22,6 +22,7 @@
 KATI_BIN_PATH ?= .
 
 KATI_CXX_SRCS := \
+	affinity.cc \
 	command.cc \
 	condvar.cc \
 	dep.cc \