filesystem: Paper over fadvise harmless failure on macos

On macos and ios, fadvise is only implemented for WillNeed and
dispatches via the system-interface crate to the F_RDADVISE fcntl.  If
you call WillNeed on an out-of-bounds offset, this fcntl returns
FileTooLarge.  Here we paper over this harmless error code to avoid this
needless platform-dependent nonuniformity.  Should fix wasmtime for
WebAssembly/wasi-testsuite#178.

Author: wingo

crates/wasi/src/filesystem.rs

@@ -751,10 +751,18 @@ impl File {
         len: u64,
         advice: system_interface::fs::Advice,
     ) -> Result<(), ErrorCode> {
+        use system_interface::fs::Advice;
         use system_interface::fs::FileIoExt as _;
-        self.run_blocking(move |f| f.advise(offset, len, advice))
-            .await?;
-        Ok(())
+        match self
+            .run_blocking(move |f| f.advise(offset, len, advice))
+            .await
+        {
+            #[cfg(any(target_os = "macos", target_os = "ios"))]
+            Error(ErrorCode::FileTooLarge) if advice == Advice::WillNeed => Ok(()),
+
+            Err(err) => Err(err.into()),
+            Ok(()) => Ok(()),
+        }
     }
 
     pub(crate) async fn set_size(&self, size: u64) -> Result<(), ErrorCode> {