Keep the map which tracks GPU kernel symbols to grow monotonically

src/program_state.cpp

@@ -444,7 +444,9 @@ const unordered_map<uintptr_t, vector<pair<hsa_agent_t, Kernel_descriptor>>>& fu
 
     auto cons = [rebuild]() {
         if (rebuild) {
-            r.clear();
+            // do NOT clear r so we reuse instances of pair<hsa_agent_t, Kernel_descriptor>
+            // created previously
+
             function_names(rebuild);
             kernels(rebuild);
             globals(rebuild);