Improved thread self test error message.

src/backend/opencl/OclLaunchData.cpp

@@ -25,6 +25,8 @@
 
 
 #include "backend/opencl/OclLaunchData.h"
+
+#include "backend/common/Tags.h"
 #include "backend/opencl/OclConfig.h"
 
 
@@ -45,3 +47,9 @@ bool xmrig::OclLaunchData::isEqual(const OclLaunchData &other) const
     return (other.algorithm == algorithm &&
             other.thread    == thread);
 }
+
+
+const char *xmrig::OclLaunchData::tag()
+{
+    return ocl_tag();
+}