move executable_cache into program_state.cpp

src/hip_hcc.cpp

@@ -2492,13 +2492,4 @@ namespace hip_impl {
         #endif
     }
 
-    std::mutex executables_cache_mutex;
-
-    std::vector<hsa_executable_t>& executables_cache(
-            std::string elf, hsa_isa_t isa, hsa_agent_t agent) {
-        static std::unordered_map<std::string,
-            std::unordered_map<hsa_isa_t,
-                std::unordered_map<hsa_agent_t, std::vector<hsa_executable_t>>>> cache;
-        return cache[elf][isa][agent];
-    }
 } // Namespace hip_impl.