Add ethosu_monitor to core_software.

Change-Id: I9423c0c2a8aca738b2788ff5c41e946432188dc3
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index abf444f..ae18806 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -21,3 +21,7 @@
 
 # Build arm_profiler
 add_subdirectory(arm_profiler)
+
+# Build ethosu_monitor
+add_subdirectory(ethosu_monitor)
+