add tuning enable variable

Add a variable that when set, enables tuning logging.  This variable is
set to false.

Tuning can be enabled via "-t" "--tuning" on the command line.
With a parameter is the path where to write the logging information.

Change-Id: I6eb8035d56cc3301face21e9375c02fc9fcc5b31
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/main.cpp b/main.cpp
index d896300..cec3789 100644
--- a/main.cpp
+++ b/main.cpp
@@ -22,6 +22,7 @@
 #include "pid/builder.hpp"
 #include "pid/buildjson.hpp"
 #include "pid/pidthread.hpp"
+#include "pid/tuning.hpp"
 #include "pid/zone.hpp"
 #include "sensors/builder.hpp"
 #include "sensors/buildjson.hpp"
@@ -65,12 +66,13 @@
         // clang-format off
         static struct option long_options[] = {
             {"conf", required_argument, 0, 'c'},
+            {"tuning", required_argument, 0, 't'},
             {0, 0, 0, 0}
         };
         // clang-format on
 
         int option_index = 0;
-        int c = getopt_long(argc, argv, "c:", long_options, &option_index);
+        int c = getopt_long(argc, argv, "t:c:", long_options, &option_index);
 
         if (c == -1)
         {
@@ -82,6 +84,10 @@
             case 'c':
                 configPath = std::string{optarg};
                 break;
+            case 't':
+                tuningLoggingEnabled = true;
+                tuningLoggingPath = std::string{optarg};
+                break;
             default:
                 /* skip garbage. */
                 continue;