Add a compile command to Wasmtime.

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
```

cranelift/codegen/src/machinst/mod.rs

@@ -69,13 +69,13 @@ use crate::value_label::ValueLabelsRanges;
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 use core::fmt::Debug;
+use core::hash::Hasher;
 use cranelift_entity::PrimaryMap;
 use regalloc::RegUsageCollector;
 use regalloc::{
     RealReg, RealRegUniverse, Reg, RegClass, RegUsageMapper, SpillSlot, VirtualReg, Writable,
 };
 use smallvec::{smallvec, SmallVec};
-use std::hash::Hasher;
 use std::string::String;
 use target_lexicon::Triple;
 
@@ -368,8 +368,13 @@ pub trait MachBackend {
     /// Return flags for this backend.
     fn flags(&self) -> &Flags;
 
-    /// Hashes all flags, both ISA-independent and ISA-specific, into the
-    /// specified hasher.
+    /// Get the enabled ISA-dependent flags that were used to make this trait object.
+    fn enabled_isa_flags(&self) -> Vec<String>;
+
+    /// Determines if the given ISA-dependent flag is enabled.
+    fn is_flag_enabled(&self, flag: &str) -> bool;
+
+    /// Hashes all flags, both ISA-independent and ISA-dependent, into the specified hasher.
     fn hash_all_flags(&self, hasher: &mut dyn Hasher);
 
     /// Return triple for this backend.