Update LLVM version from 17 to 18

[svenvh]

This will not pass out-of-tree checks until the llvm-18 packages are available on apt.llvm.org

We might also want to hold off merging this until all remaining opaque pointer changes are in (to avoid having to cherry-pick them)?

[MrSidims]

Yeah, lets wait until end of week for the merge

[MrSidims]

@svenvh probably all the required patches are merged

[svenvh]

Alright, I've created the llvm_release_170 branch now. We can't merge this PR yet, since the apt packages for llvm-18 aren't there yet.

[svenvh]

We can't merge this PR yet, since the apt packages for llvm-18 aren't there yet.

... although everyone needs the CMakeLists.txt changes to build with llvm's main. @MrSidims any preference if we merge it now, or should we separate out the CMakeLists.txt version bump (or any other ideas)?

[MrSidims]

We can't merge this PR yet, since the apt packages for llvm-18 aren't there yet.

... although everyone needs the CMakeLists.txt changes to build with llvm's main. @MrSidims any preference if we merge it now, or should we separate out the CMakeLists.txt version bump (or any other ideas)?

wouldn't https://apt.llvm.org/focal/dists/llvm-toolchain-focal/main/ contain llvm-18 already? My expectation that reverting #2104 should make CI working

[svenvh]

wouldn't https://apt.llvm.org/focal/dists/llvm-toolchain-focal/main/ contain llvm-18 already? My expectation that reverting #2104 should make CI working

Ah, I think you may be right. Let's merge this and revert #2104 then? :-)