also allow illumos to use mmap for its stack guard

Author: RalfJung

src/tools/miri/src/shims/unix/mem.rs

@@ -42,10 +42,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let map_shared = this.eval_libc_i32("MAP_SHARED");
         let map_fixed = this.eval_libc_i32("MAP_FIXED");
 
-        // This is a horrible hack, but on MacOS and Solaris the guard page mechanism uses mmap
+        // This is a horrible hack, but on MacOS and Solarish the guard page mechanism uses mmap
         // in a way we do not support. We just give it the return value it expects.
         if this.frame_in_std()
-            && matches!(&*this.tcx.sess.target.os, "macos" | "solaris")
+            && matches!(&*this.tcx.sess.target.os, "macos" | "solaris" | "illumos")
             && (flags & map_fixed) != 0
         {
             return Ok(Scalar::from_maybe_pointer(Pointer::from_addr_invalid(addr), this));