Fix panic with invalid DWARF file indices

I'm not entirely sure what causes this but Wasmtime shouldn't panic with
invalid DWARF. In general (bytecodealliance#5537) Wasmtime's support for DWARF needs to
be rewritten, but in the meantime let's play whack-a-mole with panics
and try to paper over issues.

Closes bytecodealliance#8884
Closes bytecodealliance#8904

crates/cranelift/src/debug/transform/attr.rs

@@ -116,7 +116,15 @@ where
                     ..
                 } = file_context
                 {
-                    write::AttributeValue::FileIndex(Some(file_map[(i - file_index_base) as usize]))
+                    let index = usize::try_from(i - file_index_base)
+                        .ok()
+                        .and_then(|i| file_map.get(i).copied());
+                    match index {
+                        Some(index) => write::AttributeValue::FileIndex(Some(index)),
+                        // This was seen to be invalid in #8884 and #8904 so
+                        // ignore this seemingly invalid DWARF from LLVM
+                        None => continue,
+                    }
                 } else {
                     return Err(TransformError("unexpected file index attribute").into());
                 }