enable unit-tests: enable for SensorManager

Enabled unit-tests in general for the project, and more
specifically started with a benign construction test for
the SensorManager object.

Tested: Verified continues to build and link, and unit-test
passes.
Tested: Ran on quanta-q71l board and it behaved as expected.

Change-Id: I4ad9a0c57efd0b9ccc37d26faa0cc1b82026b8d7
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sensors/builder.hpp b/sensors/builder.hpp
index 2849c71..edb30c3 100644
--- a/sensors/builder.hpp
+++ b/sensors/builder.hpp
@@ -1,7 +1,6 @@
 #pragma once
 
 #include <map>
-#include <memory>
 #include <string>
 
 #include "sensors/manager.hpp"
@@ -10,6 +9,6 @@
 /**
  * Build the sensors and associate them with a SensorManager.
  */
-std::shared_ptr<SensorManager> BuildSensors(
+SensorManager BuildSensors(
     const std::map<std::string, struct sensor>& config);