LLVM 16.0.0

[h-vetinari]

Blockers for merging this PR and thus enabling the compilers in conda-forge (indentation denotes dependency; c.f. list from 15.x):

• llvmdev v16.0.0 llvmdev-feedstock#205
  • clangdev v16.0.0 clangdev-feedstock#206
    • Build for llvm 16 cctools-and-ld64-feedstock#60
    • compiler-rt v16.0.0 compiler-rt-feedstock#63
      • Automate artefact collection; build for all VS & clang versions clang-win-activation-feedstock#18 **
      • WIP: LLVM flang 16.0.x flang-feedstock#27 **
    • libcxx v16.0.0 libcxx-feedstock#113
  • lld v16.0.0 lld-feedstock#56
  • mlir v16.0.0 mlir-feedstock#40 **
  • openmp v16.0.0 openmp-feedstock#81

The PRs marked ** are not strictly speaking necessary for merging this PR, but for LLVM 16.x support in conda-forge.

[conda-forge-webservices]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[h-vetinari]

@conda-forge/clang-compiler-activation this should be ready. Since conda-forge hasn't switched to LLVM 15 yet, I have kept 14 in the build matrix, but I expect we'll be able to drop that relatively soon.

PTAL :)