* Add egraphs option to Wasmtime config, and add it to fuzzing config generation.
This PR adds a wrapper method for Cranelift's `use_egraphs` setting to
Wasmtime's `Config`, named `cranelift_use_egraphs` analogously to its
existing `cranelift_opt_level`.
Eventually this should become a no-op as egraph-based optimization
becomes the default, but until then it makes sense to expose this as
another kind of optimization option.
This PR then adds the option to the `Arbitrary`-based config generation
for fuzzing, so compilation with egraphs will be fuzzed (on its own and
against other configurations and oracles).
* Don't use `NamedTempFile` on Windows
It looks like this prevents mmap-ing since the named temporary file
holds a `File` open which conflicts with the rights we're trying to open
the file for mmap-ing. Instead use a temporary directory to try to fix
this issue.
Co-authored-by: Alex Crichton <alex@alexcrichton.com>
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