[flang] [llvm] [flang-rt] Implement basic support for I/O from OpenMP GPU Offloading (PR #181039)

[Slava Zakharin via llvm-commits]

================
@@ -111,6 +115,12 @@ runServer(plugin::GenericDeviceTy &Device, void *Buffer,
   if (Status == rpc::RPC_UNHANDLED_OPCODE)
     Status = LIBC_NAMESPACE::shared::handle_libc_opcodes(*Port, NumLanes);
 
+#if __has_include("flang/Runtime/io-api.h")
+  if (Status == rpc::RPC_UNHANDLED_OPCODE)
+    Status = static_cast<rpc::Status>(
+        Fortran::runtime::io::IODECL(HandleRPCOpcodes)(&*Port, NumLanes));
----------------
vzakhari wrote:

```suggestion
        Fortran::runtime::io::IONAME(HandleRPCOpcodes)(&*Port, NumLanes));
```

https://github.com/llvm/llvm-project/pull/181039