I'm opening this to have something to track getting Julia updated 
and to avoid duplication of effort in case anyone else may also be 
working on updating Julia. The current version in guix is 1.6.3 
which was released almost a year ago and wasn't building for me on 
aarch64 due to https://issues.guix.gnu.org/56711 and this 
motivated me to see if I couldn't also get the most recent Julia 
to build!

The following patch is just a WIP and not in a state to merge, but 
it does build for me on aarch64 with the tests disabled. I have 
not tried running the tests yet. But I am able to install packages 
using the builtin Julia package manager which I wasn't able to do 
with guix's julia v1.6.3.

A few notes:

- Julia now appears to work with an unpatched llvm-13, however it 
  requires building llvm as a shared library with the 
  LLVM_BUILD_LLVM_DYLIB option and not the BUILD_SHARED_LIBS 
  option, however this appears to be the recommended option by the 
  llvm docs. I'm not sure if this breaks other things in guix that 
  depend on llvm. There's a possibly related issue here 
  https://issues.guix.gnu.org/42576
- I hard coded the path to the ca-certificates.crt file in guix as 
  /etc/ssl/certs/ca-certificates.crt however I suspect this is not 
  the right way to do this.

I'm sure there's other issues as well, but I'm still relatively 
new to guix, so some help in getting this polished up would be 
great! Hopefully it can be ready by the time Julia 1.8.0 is 
actually released.