## Issue Addressed
Addresses the recent CI failures caused by caching `blst` for the wrong CPU type.
## Proposed Changes
- Use `FEATURES: jemalloc,portable` when building Lighthouse & `lcli` in tests
- Add a new `TEST_FEATURES` and set to `portable` for all CI test jobs.
- Updated Makefiles to read the `TEST_FEATURES` environment variable, and default to none.