Fix redefinition of select() on platforms where ESP_PLATFORM is discarded

Ref: https://github.com/espressif/esp-idf/issues/1987

components/newlib/platform_include/sys/select.h

@@ -0,0 +1,31 @@
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef __ESP_SYS_SELECT_H__
+#define __ESP_SYS_SELECT_H__
+
+#include <sys/types.h>
+#include <sys/time.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif //__ESP_SYS_SELECT_H__