RISC V linker bug in flushInstructionCacheRISCV64
## Summary
In `flushInstructionCacheRISCV64` we have:
```
__builtin___clear_cache(codeBegin, (void*) ((uint64_t*) codeBegin + oc->fileSize));
```
Fairly sure this is wrong as it increments codeBegin not by size bytes, but by sizeOf(ptr)*size bytes due to C pointer arithmetic.
## Environment
* GHC version used:
Optional:
* Operating System:
* System Architecture:
issue