Add 3 new syscall handlers

src/windows-emulator/syscalls/file.cpp

@@ -846,4 +846,22 @@ namespace syscalls
 
         return STATUS_NOT_SUPPORTED;
     }
-}
+
+    NTSTATUS handle_NtFlushBuffersFile(const syscall_context& c, const handle file_handle,
+                                       const emulator_object<IO_STATUS_BLOCK<EmulatorTraits<Emu64>>> /*io_status_block*/)
+    {
+        if (file_handle == STDOUT_HANDLE)
+        {
+            return STATUS_SUCCESS;
+        }
+
+        const auto* f = c.proc.files.get(file_handle);
+        if (!f)
+        {
+            return STATUS_INVALID_HANDLE;
+        }
+
+        (void)fflush(f->handle);
+        return STATUS_SUCCESS;
+    }
+}