WASI prototype design, implementation, and documentation.

This adds documents describing the WASI Core API, and an implementation in
Wasmtime.

wasmtime-wasi/js-polyfill/build.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+set -euo pipefail
+
+EMCC=emcc
+
+# TODO: Remove the clang include once Emscripten supports <stdatomic.h>
+
+"$EMCC" ../sandboxed-system-primitives/src/*.c \
+    -DWASMTIME_SSP_WASI_API \
+    -DWASMTIME_SSP_STATIC_CURFDS \
+    -I../sandboxed-system-primitives/include \
+    -Iclang \
+    --shell-file shell.html \
+    polyfill.c \
+    -s WARN_ON_UNDEFINED_SYMBOLS=0 \
+    -s EXPORTED_FUNCTIONS="['_main', '_handleFiles', '___wasi_args_get', '___wasi_args_sizes_get', '___wasi_clock_res_get', '___wasi_clock_time_get', '___wasi_environ_get', '___wasi_environ_sizes_get', '___wasi_fd_prestat_get', '___wasi_fd_prestat_dir_name', '___wasi_fd_close', '___wasi_fd_datasync', '___wasi_fd_pread', '___wasi_fd_pwrite', '___wasi_fd_read', '___wasi_fd_renumber', '___wasi_fd_seek', '___wasi_fd_tell', '___wasi_fd_fdstat_get', '___wasi_fd_fdstat_set_flags', '___wasi_fd_fdstat_set_rights', '___wasi_fd_sync', '___wasi_fd_write', '___wasi_fd_advise', '___wasi_fd_allocate', '___wasi_path_create_directory', '___wasi_path_link', '___wasi_path_open', '___wasi_fd_readdir', '___wasi_path_readlink', '___wasi_path_rename', '___wasi_fd_filestat_get', '___wasi_fd_filestat_set_times', '___wasi_fd_filestat_set_size', '___wasi_path_filestat_get', '___wasi_path_filestat_set_times', '___wasi_path_symlink', '___wasi_path_unlink_file', '___wasi_path_remove_directory', '___wasi_poll_oneoff', '___wasi_proc_exit', '___wasi_proc_raise', '___wasi_random_get', '___wasi_sched_yield', '___wasi_sock_recv', '___wasi_sock_send', '___wasi_sock_shutdown']" \
+    --pre-js wasi.js \
+    -o polyfill.html