Fix configure check for zarith
Fix configure check for zarith

Fix #12938

gares/coq,silene/coq,Zimmi48/coq,ejgallego/coq,gares/coq,Zimmi48/coq,JasonGross/coq,coq/coq,Zimmi48/coq,JasonGross/coq,ejgallego/coq,SkySkimmer/coq,JasonGross/coq,JasonGross/coq,ejgallego/coq,silene/coq,SkySkimmer/coq,gares/coq,coq/coq,SkySkimmer/coq,SkySkimmer/coq,coq/coq,gares/coq,Zimmi48/coq,silene/coq,ejgallego/coq,gares/coq,coq/coq