* New upstream release
* LLVM 18 rebuild

Switch to correct SPDX license identifier and rebuild against llvm 17

New upstream release with LLVM 16

The libispcrt_static.a static lib is required by ospray during build time.

Switch to git sources to have an easier handling on vendored stuff.
Add pkgver() to properly describe pkgver.
Move cmake options to local bash array for easier handling (enabling/disabling).
Consolidate dependencies, by adding all required and removing non-required (ncurses, zlib).
Open upstream ticket about unwanted files being installed: https://github.com/ispc/ispc/issues/2482
Ping (closed) tickets about still failing tests:
https://github.com/ispc/ispc/issues/2427
https://github.com/ispc/ispc/issues/2428
https://github.com/ispc/ispc/issues/2429

New llvm broke ABI likely due to the new libstdc++ from GCC 12:

undefined symbol: _ZNKSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE7compareEPKc, version LLVM_13

Upstream patch to remove support for very old llvm (<6)
Upstream patch based on previous one to add support for llvm 10
Distro patch to support unified libclang-cpp.so

Required to redo LLVM6 compatibility in order to apply properly LLVM7 one.

Fix compiling with our LLVM by using Fedora patch.

FTR, commands used to change arch=() and then verify the changes:

$ sed -Ei "/^arch=/{s/ *?['\"]?i686['\"]? *?//;s/ *$//}" */*/PKGBUILD*

$ grep -r i686 * | grep arch= | grep -v repos

$ svn diff | grep -A 1 ^-[^-] | grep -v -- -- | cut -c2- |
  while IFS=$'\n' read -r l1; IFS=$'\n' read -r l2; do
    echo "$l1 -> $l2"
  done | sort -u