chore(frontends/lean/decl_cmds): disable incorrect warning message produced by gcc
chore(frontends/lean/decl_cmds): disable incorrect warning message produced by gcc

soonhokong/lean-osx,UlrikBuchholtz/lean,rlewis1988/lean,fpvandoorn/lean2,leanprover-community/lean,soonhokong/lean,fpvandoorn/lean,leodemoura/lean,c-cube/lean,UlrikBuchholtz/lean,digama0/lean,leanprover/lean,fgdorais/lean,avigad/lean,fpvandoorn/lean2,levnach/lean,leanprover/lean,fpvandoorn/lean2,soonhokong/lean-windows,eigengrau/lean,fpvandoorn/lean,johoelzl/lean,digama0/lean,leanprover/lean,leodemoura/lean,htzh/lean,sp3ctum/lean,soonhokong/lean-osx,johoelzl/lean,sp3ctum/lean,soonhokong/lean-osx,c-cube/lean,soonhokong/lean-windows,htzh/lean,sp3ctum/lean,fgdorais/lean,leodemoura/lean,levnach/lean,Kha/lean,Kha/lean,avigad/lean,digama0/lean,johoelzl/lean,dselsam/lean,htzh/lean,rlewis1988/lean,sp3ctum/lean,javra/lean,soonhokong/lean-osx,avigad/lean,soonhokong/lean-windows,leanprover-community/lean,fpvandoorn/lean,dselsam/lean,johoelzl/lean,Kha/lean,soonhokong/lean,leanprover/lean,avigad/lean,soonhokong/lean-windows,soonhokong/lean,leodemoura/lean,sp3ctum/lean,fgdorais/lean,eigengrau/lean,javra/lean,dselsam/lean,Kha/lean,fgdorais/lean,leodemoura/lean,UlrikBuchholtz/lean,levnach/lean,c-cube/lean,dselsam/lean,rlewis1988/lean,javra/lean,avigad/lean,UlrikBuchholtz/lean,dselsam/lean,levnach/lean,fpvandoorn/lean2,htzh/lean,soonhokong/lean-osx,rlewis1988/lean,digama0/lean,javra/lean,dselsam/lean,javra/lean,johoelzl/lean,htzh/lean,eigengrau/lean,Kha/lean,eigengrau/lean,soonhokong/lean,digama0/lean,fpvandoorn/lean2,UlrikBuchholtz/lean,leanprover-community/lean,leanprover/lean,rlewis1988/lean,leanprover/lean,fpvandoorn/lean,leanprover-community/lean,soonhokong/lean,c-cube/lean,fgdorais/lean,leanprover-community/lean,fpvandoorn/lean,Kha/lean,digama0/lean,levnach/lean,c-cube/lean,johoelzl/lean,avigad/lean,fgdorais/lean,soonhokong/lean-windows,fpvandoorn/lean,eigengrau/lean,rlewis1988/lean,leodemoura/lean,leanprover-community/lean