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.
MASM (Microsoft Macro Assembler) needs to be enabled to successfully
compile .asm files on Windows. Without enabling this language
automatically in runtime_lib.cmake, Windows cmake projects using WAMR
get hard-to-diagnose linker errors about missing symbols as the assembly
file is not compiled at all.
To make it clearer to users when synchronization behaviour is not
supported, return ENOTSUP when O_RSYNC, O_DSYNC or O_SYNC are
respectively not defined. Linux also doesn't support O_RSYNC despite the
O_RSYNC flag being defined.
Return a WASI error code (rather than a host POSIX one). In addition,
there is no need to return an error in the case that the provided buffer
is too large.
The WASI docs allow for fewer rights to be applied to an fd than requested but
not more. This behavior is also asserted in the rust WASI tests, so it's necessary
for those to pass as well.
