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/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c

@@ -685,9 +685,20 @@ fd_table_insert_existing(struct fd_table *ft, __wasi_fd_t in, int out)
     struct fd_object *fo;
     __wasi_errno_t error;
 
-    if (fd_determine_type_rights(out, &type, &rights_base, &rights_inheriting)
-        != 0)
+    error =
+        fd_determine_type_rights(out, &type, &rights_base, &rights_inheriting);
+    if (error != 0) {
+#ifdef BH_PLATFORM_EGO
+        /**
+         * since it is an already opened file and we can assume the opened file
+         * has all necessary rights no matter how to get
+         */
+        if (error != __WASI_ENOTSUP)
+            return false;
+#else
         return false;
+#endif
+    }
 
     error = fd_object_new(type, &fo);
     if (error != 0)

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
+)