perf(library/type_context): move check_system to strategic places
perf(library/type_context): move check_system to strategic places

levnach/lean,levnach/lean,avigad/lean,johoelzl/lean,soonhokong/lean-windows,soonhokong/lean-windows,leanprover-community/lean,leanprover-community/lean,fgdorais/lean,rlewis1988/lean,fpvandoorn/lean2,leanprover-community/lean,soonhokong/lean-osx,fgdorais/lean,rlewis1988/lean,soonhokong/lean-osx,leodemoura/lean,fpvandoorn/lean,avigad/lean,Kha/lean,leodemoura/lean,dselsam/lean,leanprover/lean,avigad/lean,fgdorais/lean,fgdorais/lean,soonhokong/lean-windows,soonhokong/lean,rlewis1988/lean,Kha/lean,levnach/lean,javra/lean,leanprover-community/lean,leanprover-community/lean,fpvandoorn/lean,javra/lean,soonhokong/lean,javra/lean,leanprover-community/lean,leanprover/lean,Kha/lean,fpvandoorn/lean2,rlewis1988/lean,fpvandoorn/lean,Kha/lean,digama0/lean,fpvandoorn/lean2,avigad/lean,johoelzl/lean,fpvandoorn/lean,leanprover/lean,soonhokong/lean,johoelzl/lean,soonhokong/lean-windows,fpvandoorn/lean2,avigad/lean,soonhokong/lean,Kha/lean,dselsam/lean,levnach/lean,UlrikBuchholtz/lean,leanprover/lean,soonhokong/lean-osx,dselsam/lean,digama0/lean,soonhokong/lean-osx,dselsam/lean,fgdorais/lean,UlrikBuchholtz/lean,digama0/lean,UlrikBuchholtz/lean,dselsam/lean,dselsam/lean,johoelzl/lean,fpvandoorn/lean,soonhokong/lean,leodemoura/lean,leodemoura/lean,avigad/lean,digama0/lean,leanprover/lean,leodemoura/lean,javra/lean,leanprover/lean,johoelzl/lean,digama0/lean,javra/lean,fpvandoorn/lean2,levnach/lean,fgdorais/lean,UlrikBuchholtz/lean,rlewis1988/lean,UlrikBuchholtz/lean,Kha/lean,leodemoura/lean,fpvandoorn/lean,soonhokong/lean-osx,soonhokong/lean-windows,rlewis1988/lean,digama0/lean,johoelzl/lean