can't move to latest version of llvm on ghc 9.12.2

[George Colpitts]

llvm 20 is out but unlike in earlier versions of ghc moving to it means you
can no longer use llvm:

compiling:

ghc -fllvm hello.hs
Loaded package environment from
/Users/avie/.ghc/aarch64-darwin-9.12.2/environments/default
[1 of 2] Compiling Main             ( hello.hs, hello.o )
<no location info>: error: [GHC-66599]
    GHC was not configured with a supported LLVM toolchain
    Make sure you have installed LLVM between [13 and 20) and reinstall GHC
to make -fllvm work


from configure:

configure: We only support llvm 13 upto 20 (non-inclusive) (found 20.1.1).


Can we move to llvm 20 on HEAD and can we revert to the old behavior on ghc
9.12.3?

Should I file an ER?

Thanks
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