ghc-bignum-1.1 bump on 9.0 branch breaks agda build.

<command line>: libHSghc-bignum-1.0-ghc9.0.1.so: cannot open shared object file: No such file or directory
cabal: Failed to build Agda-2.6.1.3 (which is required by test-Agda-1.0). Se

If I try and build Agda with the latest bindist from the 9.0 branch then I get an error like this:

ghc-pkg list tells me:

[nix-shell:~/head.hackage]$ ghc/bin/ghc-pkg list
/nix/store/49mhbl1883nbi5lcaxpvl69d6y5p4l9b-ghc-9.0.1/lib/ghc-9.0.1/package.conf.d
    Cabal-3.4.0.0
    array-0.5.4.0
    base-4.15.0.0
    binary-0.8.8.0
    bytestring-0.10.12.1
    containers-0.6.4.1
    deepseq-1.4.5.0
    directory-1.3.6.1
    exceptions-0.10.4
    filepath-1.4.2.1
    ghc-9.0.1
    ghc-bignum-1.1
    ghc-boot-9.0.1
    ghc-boot-th-9.0.1
    ghc-compact-0.1.0.0
    ghc-heap-9.0.1
    ghc-prim-0.7.0
    ghci-9.0.1
    haskeline-0.8.1.0
    hpc-0.6.1.0
    integer-gmp-1.1
    libiserv-9.0.1
    mtl-2.2.2
    parsec-3.1.14.0
    pretty-1.1.3.6
    process-1.6.11.0
    rts-1.0.2
    stm-2.5.0.0
    template-haskell-2.17.0.0
    terminfo-0.4.1.4
    text-1.2.4.1
    time-1.9.3
    transformers-0.5.6.2
    unix-2.7.2.2
    xhtml-3000.2.2.1

Perhaps the issue is that the branch stil has RELEASE=YES set?

@wz1000