ghc-8.10.5 documentation states its needed LLVM 9 for llvm backend but compiler warns its unsupported
```
[ 58s] checking llc version (9.0.1) is between 10 and 12... no
[ 58s] configure: We only support llvm 10 to 12 (found 9.0.1).
[ 58s] checking for opt-12... no
[ 58s] checking for opt-12.0... no
[ 58s] checking for opt-11... no
[ 58s] checking for opt-11.0... no
[ 58s] checking for opt-10... no
[ 58s] checking for opt-10.0... no
[ 58s] checking for opt... opt
[ 58s] checking opt version (9.0.1) is between 10 and 12... no
[ 58s] configure: We only support llvm 10 to 12 (found 9.0.1).
```
issue