Support LLVM 16

[HertzDevil]

Tested on x86_64-linux-gnu for some build between 16.0.0-rc3 and rc4 only. No changes were required in the compiler at all because we already switched to opaque pointers for LLVM 15.

This does not include the debug information stuff in #13174.

[HertzDevil]

This workaround:

crystal/.github/workflows/win.yml

Lines 309 to 313 in 3a360b1

	- name: Patch LLVM for VS 2019 16.7.0
	working-directory: ./llvm-src
	if: steps.cache-llvm.outputs.cache-hit != 'true'
	run: |
	sed -i 's/#ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE/#if 0/' include/llvm/Support/type_traits.h

is also unnecessary for LLVM 16 due to https://reviews.llvm.org/rG36357c967cdb9006dd7de9be0dd52068da2a4f96

[HertzDevil]

/mnt/llvm/bin/llvm-config: error while loading shared libraries: libtinfo.so.5: cannot open shared object file: No such file or directory

🤔

[straight-shoota]

🚀

[HertzDevil]

It looks like both the 16.0.2 and 16.0.3 packages work. I could reproduce the crash locally with 16.0.0 but still have no clue what was going on. C++ ABI mismatch...?

EDIT: it is probably due to a missing LD_LIBRARY_PATH

[beta-ziliani]

Why are these in 18.04? Don't they work in 20.04? 18.04 is close to EOL

[HertzDevil]

That's the version number that comes with the LLVM download, our base image is now always 22.04