nightly-2021-07-21

Changes since nightly-2021-07-20:

Full commit log

• 0943dc3 chore: update stage0
• a019d80 chore: document simplified object header and remove obsolete cmake options
• 10122ba chore: try to fix compilation error at CI
• 286136b fix: missing std::
• fa8b842 chore: update stage0
• c59e72a chore: cleaner lean_dec_ref, inline persistent object case
• da66610 chore: cleanup
• 974caa9 chore: typo
• e0132ea chore: update stage0
• 489b280 feat: simpler and faster RC