Comment 2 for bug 1860575

The error message is a rather cryptic "LLVM ERROR: 64-bit code requested on a subtarget
that doesn't support it!" as it knows Athlon CPUs don't support the AMD64 ISA.

I will relay the tip to the people managing the VMs, I guess this problem went unnoticed
for so long because there are not many `qemu64` users.

I'm available to test a patch whenever it becomes available, I didn't directly send one
because I was afraid of breaking the backward compatibility and some (many?) VMs.