forked from boostorg/core
Properly set BUILD_JOBS environment variable in CMake-related jobs as it is used in build and run steps. Without the variable being set, -j without a number means "no limit on the number of jobs", which may hit system resource limits and cause the job to fail. Also, Mac OS seem to sometimes hang on too many parallel build jobs, even if BUILD_JOBS is specified correctly. So disable parallel builds for now. Additionally, use GIT_FETCH_JOBS universally.