Both, clang and llvm, version 15.0.0 now pull in dev-python/sphinx, even without `doc` USE flag. Version 14 of the toolchain worked fine without sphinx. I do not see anything in the ebuild that would explain this difference in behaviour. I will attach the output of emerge --info for llvm and clang.
Created attachment 803236 [details] clang_info emerge --info for sys-devel/clang
Created attachment 803239 [details] emerge --info for sys-devel/llvm
From llvm.org.eclass: ``` # @ECLASS_VARIABLE: _LLVM_NEWEST_MANPAGE_RELEASE # @INTERNAL # @DESCRIPTION: # The newest release of LLVM for which manpages were generated. _LLVM_NEWEST_MANPAGE_RELEASE=14.0.6 ``` They'll be generated for the keyworded, non-RC versions.