fix(util/thread): detach unjoined threads
fix(util/thread): detach unjoined threads

Kha/lean,dselsam/lean,Kha/lean,johoelzl/lean,fpvandoorn/lean,johoelzl/lean,leanprover/lean,avigad/lean,digama0/lean,dselsam/lean,leanprover-community/lean,leodemoura/lean,leanprover-community/lean,leanprover-community/lean,leodemoura/lean,johoelzl/lean,leodemoura/lean,dselsam/lean,digama0/lean,avigad/lean,Kha/lean,leanprover-community/lean,leanprover/lean,dselsam/lean,digama0/lean,leanprover-community/lean,leodemoura/lean,leanprover/lean,Kha/lean,digama0/lean,rlewis1988/lean,johoelzl/lean,Kha/lean,leanprover/lean,digama0/lean,dselsam/lean,leanprover/lean,johoelzl/lean,rlewis1988/lean,leanprover-community/lean,avigad/lean,leodemoura/lean,fpvandoorn/lean,fpvandoorn/lean,fpvandoorn/lean,digama0/lean,avigad/lean,leodemoura/lean,leanprover/lean,johoelzl/lean,dselsam/lean,avigad/lean,avigad/lean,rlewis1988/lean,fpvandoorn/lean,Kha/lean,rlewis1988/lean,rlewis1988/lean,fpvandoorn/lean,rlewis1988/lean