Use environment variables

Prefer environment variables over hardcoded paths and configuration values in build scripts and configuration files. This approach improves portability, flexibility, and maintainability by allowing different environments to specify their own paths without modifying the codebase.

Instead of hardcoding paths like:

set(oneCCL_DIR "/opt/intel/oneapi/ccl/latest/lib/cmake/oneCCL")
set(MPI_INCLUDE_PATH "/opt/intel/oneapi/mpi/latest/include")

Use environment variables:

set(oneCCL_DIR "$ENV{ONEAPI_ROOT}/ccl/latest/lib/cmake/oneCCL")
set(MPI_INCLUDE_PATH "$ENV{ONEAPI_ROOT}/mpi/latest/include")

For debug options and feature flags, check environment variables instead of adding compile-time options. This allows runtime configuration without rebuilding and follows established patterns like GGML_SCHED_DEBUG. Environment variables make configurations more flexible across different deployment environments and reduce the need for environment-specific build modifications.