Ensure feature parity for cmake with Makefile#5582

Draft

vtjnash wants to merge 2 commits intoOpenMathLib:developfrom

vtjnash:jn/cmake-all

Commits on Dec 23, 2025

cmake: document options and set defaults for influential variables

vtjnash
and
claude
committed
cmake: add THREAD_TIMEOUT, prevent in-tree builds, fix ARCH handling

vtjnash
and
claude
committed