Make a workaround for EGO when fstat returns NOT_SUPPORT (#1970)

The problem was found by a `Golang + WAMR (as CGO)` wrapped by EGO
in SGX Enclave.

`fstat()` in EGO returns dummy values:
- EGO uses a `mount` configuration to define the mount points that apply
  the host file system presented to the Encalve.
- EGO has a different programming model: the entire application runs inside
  the enclave. Manual ECALLs/OCALLs by application code are neither
  required nor possible.

Add platform ego and add macro control for the return value checking of
`fd_determine_type_rights` in libc-wasi to resolve the issue.

core/shared/platform/ego/platform_init.c

@@ -0,0 +1,6 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include "../linux/platform_init.c"

core/shared/platform/ego/platform_internal.h

@@ -0,0 +1,6 @@
+/*
+ * Copyright (C) 2019 Intel Corporation.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include "../linux/platform_internal.h"

core/shared/platform/ego/shared_platform.cmake

@@ -0,0 +1,20 @@
+# Copyright (C) 2019 Intel Corporation.  All rights reserved.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+set (PLATFORM_SHARED_DIR ${CMAKE_CURRENT_LIST_DIR})
+
+add_definitions(-DBH_PLATFORM_EGO)
+
+include_directories(${PLATFORM_SHARED_DIR})
+include_directories(${PLATFORM_SHARED_DIR}/../include)
+
+include (${CMAKE_CURRENT_LIST_DIR}/../common/posix/platform_api_posix.cmake)
+
+set (PLATFORM_SHARED_SOURCE
+  ${PLATFORM_COMMON_POSIX_SOURCE}
+  ${CMAKE_CURRENT_LIST_DIR}/platform_init.c
+)
+
+LIST (APPEND RUNTIME_LIB_HEADER_LIST
+  ${CMAKE_CURRENT_LIST_DIR}/platform_internal.h
+)