OSL v1.12.11.0

Release 1.12.11.0 -- 5 Apr 2023 (compared to 1.12.10.0)

• Build: Add Qt 6.x compatibility (Qt is only used for osltoy). #1655
• Build: more careful about paths to look for LLVM. #1656
• Build: Fix Cuda compilation flags for LLVM 15. #1659
• Notice: OSL does not yet build properly against the newly release LLVM 16.
  You must use LLVM 9-15. For Mac users who get their llvm from Homebrew,
  please be aware that Homebrew has changed its default llvm to 16, so you'll
  need to brew install llvm@14 and make your OSL CMake define:
  -DLLVM_ROOT=/usr/local/opt/llvm@14