This resolves T83631
sometimes bumping a version is just editing versions.cmake and that's it, this howerver is not one of those cases, OSL made some rather significant changes to their build system (for the better) and turned the previous soft dependency on clang now a hard dependency (they dropped boost wave support) which snowballed a little into other deps.
OSL Expects clang/llvm to live in a single folder, convincing OSL that is not the case seems more work than actually making clang/llvm build together so this is addressed as well.
Included in this diff:
-OSL Update to 1.11.10.0
-refactor the llvm/clang/clang-tools-extra builds into the llvm build using the llvm-project tarball for building that has all of the subprojects in it.
-update ispc/openmp builds since clang no longer its own dependency and they have to depend on the llvm build now.
-Update the windows builder to use the 64 bit host tools since it ran out of ram linking clang
-Since OSL now needs clang to link successfully a findclang.cmake has been provided for linux/mac, I know for sure it links blender on linux at this point, it may or may not need additional tweaks to build/link D9465 and/or mac.
I'm somewhat divided on combining all of this into a single diff, they seem independend things, on the other hand they are also fully dependend on each other, and you cannot roll back one without having to roll back all others as well, so for that reason I have combined all into a single diff
builds and passes all tests on both windows and linux, was not able to test on mac, and I'm not entirely sure I didn't make any mistakes in the refactor of clang-tools-extra (which only builds on mac) so mac maintainers keep an eye on that!
review/test only at this point, landing may be a little tricky, keeping it all in one diff makes sense, however landing the clang stuff first would make things a lot eaiser though.. still torn there..
Note: There is a boost update in T83246: VFX Reference Platform 2021 Compatibility so this should be landing after that to prevent multiple updates of the same lib