New comment by ericonr on void-packages repository

https://github.com/void-linux/void-packages/pull/26928#issuecomment-739381463

Comment:
Has cross failures:

```
checking for shm_open in -lrt... yes
checking for shm_open in -lroot... no
checking for __shm_open in -lroot... no
checking for mmap() using shm_open() shared memory support... no
configure: error: No supported shared memory caching support was found when configuring opcache. Check config.log for any errors or missing dependencies.
```

Might be something worth adding to autoconfigure cache, or just as an option here.