Abstract POSIX filesystem functions (#2585)

To allow non-POSIX platforms such as Windows to support WASI libc
filesystem functionality, create a set of wrapper functions which provide a
platform-agnostic interface to interact with the host filesystem. For now,
the Windows implementation is stubbed but this will be implemented
properly in a future PR. There are no functional changes in this change,
just a reorganization of code to move any direct POSIX references out of
posix.c in the libc implementation into posix_file.c under the shared
POSIX sources.

See https://github.com/bytecodealliance/wasm-micro-runtime/issues/2495 for a
more detailed overview of the plan to port the WASI libc filesystem to Windows.

core/shared/platform/linux-sgx/platform_internal.h

@@ -69,6 +69,10 @@ strcpy(char *dest, const char *src);
 #define os_memory_order_seq_cst __ATOMIC_SEQ_CST
 #define os_atomic_thread_fence __atomic_thread_fence
 
+typedef int os_file_handle;
+typedef DIR *os_dir_stream;
+typedef int os_raw_file_handle;
+
 #ifdef __cplusplus
 }
 #endif

core/shared/platform/linux-sgx/sgx_ipfs.h

@@ -7,7 +7,6 @@
 #define _LIBC_WASI_SGX_PFS_H
 
 #include "bh_hashmap.h"
-#include "wasmtime_ssp.h"
 
 #ifdef __cplusplus
 extern "C" {

core/shared/platform/linux-sgx/shared_platform.cmake

@@ -20,16 +20,20 @@ if (NOT BUILD_UNTRUST_PART EQUAL 1)
                        ${SGX_SDK_DIR}/include/libcxx)
 endif ()
 
-if (NOT WAMR_BUILD_LIBC_WASI EQUAL 1)
-  add_definitions(-DSGX_DISABLE_WASI)
-endif ()
-
 if (NOT WAMR_BUILD_THREAD_MGR EQUAL 1)
   add_definitions(-DSGX_DISABLE_PTHREAD)
 endif ()
 
 file (GLOB source_all ${PLATFORM_SHARED_DIR}/*.c)
 
+if (NOT WAMR_BUILD_LIBC_WASI EQUAL 1)
+  add_definitions(-DSGX_DISABLE_WASI)
+else()
+  list(APPEND source_all ${PLATFORM_SHARED_DIR}/../common/posix/posix_file.c)
+  include (${CMAKE_CURRENT_LIST_DIR}/../common/libc-util/platform_common_libc_util.cmake)
+  set(source_all ${source_all} ${PLATFORM_COMMON_LIBC_UTIL_SOURCE})
+endif()
+
 file (GLOB source_all_untrusted ${PLATFORM_SHARED_DIR}/untrusted/*.c)
 
 set (PLATFORM_SHARED_SOURCE ${source_all})