Windows support

[cjihrig]

There are a number of TODO comments sprinkled throughout the code. A number of them are Windows specific. The most important are probably in uvwasi__is_absolute_path() and uvwasi__resolve_path(). Once those ones are resolved there will still be some Windows limitations, but libuv should smooth out most of them.

[gengjiawen]

https://github.com/cjihrig/uvwasi/blob/e5e168e4516e960c363c93bd438f254968f19ed0/src/fd_table.c#L117-L123

Six macros is not support on windows. See #27 (comment).

[tniessen]

@gengjiawen Possible fix in #30. Obviously won't work for sockets etc.

[gengjiawen]

@gengjiawen Possible fix in #30. Obviously won't work for sockets etc.

Yeap. Other macros works in mingw except S_ISSOCK.

[cjihrig]

Current state of known Windows issues:

• fd_fdstat_get() sets the resulting uvwasi_fdstat_t's fs_flags field to 0. This can be improved.
• fd_fdstat_set_flags() is not supported on Windows. I'm not sure if this can be improved.
• fd_readdir() does not currently work on Windows. The API itself is awkward here, but support can be improved here (but might require not using libuv).
• poll_oneoff() is not implemented on Windows or any other platform yet. poll_oneoff() is implemented, but only supports sockets due to it's use of uv_poll_t.

[Paril]

Non-console executables don't have stdin/out/err which causes uvwasi__insert_stdio to fail. Ideally there should be a flag to exclude these/void them out.

[BambiHaber]

Just a simple question, why not add an #ifdef for win32 and add simple validation at the libuv wrapper, which would try at first to create the original string, and if failed, then bubble up an exception (assuming that maybe someday ":" would be supported by windows system? I hope this sounds somewhat reasonable - since I haven't dived into the libuv wrapper. but this seems like a solution that would span a solution on multiple environments as long as they're windows ( if when comes a day where windows FS allows ":")