How do I get GHC for CentOS 7 aarch64?

The problem:

• Our project needs GHC 9.0.2, and we need to build it on CentOS 7 aarch64
• Upgrading the OS is not an option, and ideally we would make it easy to distribute to all our devs (i.e. just distribute the GHC binary-dist, without also needing to distribute newer glibc's)
• The GHC 9.0.2 aarch64 binary links to glibc 2.27, but CentOS 7 has glibc 2.17
• CentOS 7 provides GHC 7.6 via yum

What we've tried:

• Use GHC 7.6 to build 7.8 (and build our way up)
  • Building 7.8 immediately gives "Unknown arch aarch64"
• Install GHC 8.0 in Ubuntu bionic (which is also glibc 2.17) to build 8.4 (and build our way up), then copy the binary-dist into CentOS 7
  • This gave us errors like

    /tmp/ghc31887_0/ghc_3.hc:22:6: error:
         error: ‘ghczmprim_GHCziTypes_Module_static_info’ undeclared here (not in a function)
         (W_)&ghczmprim_GHCziTypes_Module_static_info, ((W_)&ghc_GhcPrelude_zdtrModule2_closure+1), ((W_)&ghc_GhcPrelude_zdtrModule1_closure+1), 0x3UL
              ^
    
    /tmp/ghc31887_0/ghc_3.hc:22:1: error:
         error: initializer element is not constant
         (W_)&ghczmprim_GHCziTypes_Module_static_info, ((W_)&ghc_GhcPrelude_zdtrModule2_closure+1), ((W_)&ghc_GhcPrelude_zdtrModule1_closure+1), 0x3UL
         ^
    
    /tmp/ghc31887_0/ghc_3.hc:22:1: error:
         error: (near initialization for ‘ghc_GhcPrelude_zdtrModule_closure[0]’)
    `gcc' failed in phase `C Compiler'. (Exit code: 1)
    <<ghc: 108215128 bytes, 48 GCs, 5744830/10695440 avg/max bytes residency (4 samples), 32M in use, 0.001 INIT (0.001 elapsed), 0.068 MUT (0.093 elapsed), 0.040 GC (0.040 elapsed) :ghc>>
    make[1]: *** [compiler/ghc.mk:446: compiler/stage1/build/GhcPrelude.o] Error 1
    make: *** [Makefile:125: all] Error 2

• Use GHC 9.0 from Nix and rebuild GHC 9.0
  • The rebuilt GHC 9.0 still links to Nix libc
  • We don't want to force all devs to install Nix just for this
• Build glibc 2.27 on CentOS7, and installing GHC 9.0 from the aarch64 bindist using the new glibc
  • This involved rebuilding gcc + glibc
  • Got failures invoking ghc-cabal-bindist linked to the new glibc

I know about this doc: https://gitlab.haskell.org/ghc/ghc/-/wikis/building/cross-compiling. I could try building on a new CentOS Stream aarch64 system and cross compile to an older glibc, but I'm not sure how to link the older glibc. I could also try building on CentOS 7 x86_64 and cross compile to aarch64, but I don't know how to do this. The doc just says "get a C compiler that can generate code for the target platform", but I'm not sure how to get such a compiler.

Reddit thread: https://www.reddit.com/r/haskell/comments/123wz5x/help_building_ghc_for_centos_7_aarch64/