CI: Use LLVM's OpenMP over MSVC_DEBUG_non_redist on Windows (#26678)
* CI: Use LLVM's OpenMP over MSFT_DEBUG_non_redist on Windows
Currently, we ship the non-redist debug version of microsoft's libomp.
This PR changes this to official LLVM's release, also packaging
the license as needed.
* Remove LLVM SHA from job name to increase legibility
* Add temp validations to CI
* Revert "Add temp validations to CI"
This reverts commit eef97c88b5bac280803ebb3c3b7bb09f89b0fd88.
* Build OpenMP in CI
* Make OpenMP fetch self-contained in cmake and cache in CI
* Robustify Licens-packaging
1. Ship OpenMP license, not LLVM's.
2. Invalidate cache also on checksum of the license
* Remove stale reference in docs/build.md
* No longer package base license in release
This was scope-creep
* Add explanatory comment to OpenMP license
* Remove arm64 smoke
Forgot this during conflict resolution during rebase of
c54c0e9cf6030a5a54ce8bdd81b3e146d9787d42
* Remove GGML_OPENMP_FETCH_CACHE_DIR as requested by @CISC
* whitespace changes