This commit adds a `compile` command to the Wasmtime CLI.
The command can be used to Ahead-Of-Time (AOT) compile WebAssembly modules.
With the `all-arch` feature enabled, AOT compilation can be performed for
non-native architectures (i.e. cross-compilation).
The `Module::compile` method has been added to perform AOT compilation.
A few of the CLI flags relating to "on by default" Wasm features have been
changed to be "--disable-XYZ" flags.
A simple example of using the `wasmtime compile` command:
```text
$ wasmtime compile input.wasm
$ wasmtime input.cwasm
```
This commit moves all of the caching support that currently lives in
`wasmtime-environ` into a `wasmtime-cache` crate and makes it optional. The
goal here is to slim down the `wasmtime-environ` crate and clearly separate
boundaries where caching is a standalone and optional feature, not intertwined
with other crates.
This commit refactors the Wasmtime CLI tools to use `structopt` instead of
`docopt`.
The `wasmtime` tool now has the following subcommands:
* `config new` - creates a new Wasmtime configuration file.
* `run` - runs a WebAssembly module.
* `wasm2obj` - translates a Wasm module to native object file.
* `wast` - runs a test script file.
If no subcommand is specified, the `run` subcommand is used. Thus,
`wasmtime foo.wasm` should continue to function as expected.
The `wasm2obj` and `wast` tools still exist, but delegate to the same
implementation as the `wasmtime` subcommands. The standalone `wasm2obj` and
`wast` tools may be removed in the future in favor of simply using `wasmtime`.
Included in this commit is a breaking change to the default Wasmtime
configuration file: it has been renamed from `wasmtime-cache-config.toml` to
simply `config.toml`. The new name is less specific which will allow for
additional (non-cache-related) settings in the future.
There are some breaking changes to improve command line UX:
* The `--cache-config` option has been renamed to `--config`.
* The `--create-config-file` option has moved to the `config new` subcommand.
As a result, the `wasm2obj` and `wast` tools cannot be used to create a new
config file.
* The short form of the `--optimize` option has changed from
`-o` to `-O` for consistency.
* The `wasm2obj` command takes the output object file as a
required positional argument rather than the former required output *option*
(e.g. `wasmtime wasm2obj foo.wasm foo.obj`).
