feat(library/app_builder): mk_app with mask
feat(library/app_builder): mk_app with mask

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