Fuzzing: add use_egraphs option back to fuzzing config generator. (#5388)

This PR reverts #5128 (commit b3333bf9ea),
adding back the ability for the fuzzing config generator to set
the `use_egraphs` Cranelift option. This will start to fuzz the
egraphs-based optimization framework again, now that #5382 has landed.

cranelift/fuzzgen/src/lib.rs

@@ -253,6 +253,7 @@ where
             "enable_incremental_compilation_cache_checks",
             "regalloc_checker",
             "enable_llvm_abi_extensions",
+            "use_egraphs",
         ];
         for flag_name in bool_settings {
             let enabled = self

crates/fuzzing/src/generators/config.rs

@@ -140,6 +140,7 @@ impl Config {
             .native_unwind_info(self.wasmtime.native_unwind_info)
             .cranelift_nan_canonicalization(self.wasmtime.canonicalize_nans)
             .cranelift_opt_level(self.wasmtime.opt_level.to_wasmtime())
+            .cranelift_use_egraphs(self.wasmtime.use_egraphs)
             .consume_fuel(self.wasmtime.consume_fuel)
             .epoch_interruption(self.wasmtime.epoch_interruption)
             .memory_init_cow(self.wasmtime.memory_init_cow)
@@ -336,6 +337,7 @@ impl<'a> Arbitrary<'a> for Config {
 #[derive(Arbitrary, Clone, Debug, Eq, Hash, PartialEq)]
 pub struct WasmtimeConfig {
     opt_level: OptLevel,
+    use_egraphs: bool,
     debug_info: bool,
     canonicalize_nans: bool,
     interruptable: bool,