Now that we are going to be updating the JIT to use LLVM 19 (see#124093), we can use thepreserve_none attribute which exposes ghccc to the compiler instead ofmanually patching in the calling convention in LLVM IR and then compiling that. Additionally,preserve_none supports bothx86-64 andAArch64 targets.

Will need to see what happens with 32-bit Windows during CI.

Linked PRs

• gh-125498: Update JIT builds to use LLVM 19 and usepreserve_none #125499