BLD: fix Qhull build issue with MinGW-w64.  Closes gh-3237.
BLD: fix Qhull build issue with MinGW-w64.  Closes gh-3237.

Thanks to Carl Kleffner.

vhaasteren/scipy,zerothi/scipy,maciejkula/scipy,behzadnouri/scipy,mingwpy/scipy,tylerjereddy/scipy,kalvdans/scipy,pnedunuri/scipy,felipebetancur/scipy,futurulus/scipy,gef756/scipy,rmcgibbo/scipy,mortonjt/scipy,perimosocordiae/scipy,witcxc/scipy,pschella/scipy,jor-/scipy,maniteja123/scipy,mdhaber/scipy,matthew-brett/scipy,mhogg/scipy,sonnyhu/scipy,mingwpy/scipy,mtrbean/scipy,mdhaber/scipy,Dapid/scipy,sriki18/scipy,niknow/scipy,gef756/scipy,trankmichael/scipy,vberaudi/scipy,endolith/scipy,ortylp/scipy,kalvdans/scipy,rgommers/scipy,nmayorov/scipy,bkendzior/scipy,vanpact/scipy,rmcgibbo/scipy,aman-iitj/scipy,piyush0609/scipy,rgommers/scipy,gfyoung/scipy,sauliusl/scipy,Dapid/scipy,WarrenWeckesser/scipy,josephcslater/scipy,andyfaff/scipy,e-q/scipy,jonycgn/scipy,dominicelse/scipy,niknow/scipy,zxsted/scipy,piyush0609/scipy,ortylp/scipy,vberaudi/scipy,gef756/scipy,scipy/scipy,Kamp9/scipy,efiring/scipy,ilayn/scipy,pbrod/scipy,jor-/scipy,WillieMaddox/scipy,gfyoung/scipy,Newman101/scipy,jakevdp/scipy,Srisai85/scipy,apbard/scipy,hainm/scipy,anielsen001/scipy,vhaasteren/scipy,ortylp/scipy,andim/scipy,andyfaff/scipy,mikebenfield/scipy,Kamp9/scipy,Gillu13/scipy,mhogg/scipy,pizzathief/scipy,vberaudi/scipy,anielsen001/scipy,Srisai85/scipy,mortada/scipy,sauliusl/scipy,vhaasteren/scipy,pbrod/scipy,Stefan-Endres/scipy,nonhermitian/scipy,sriki18/scipy,njwilson23/scipy,behzadnouri/scipy,Eric89GXL/scipy,efiring/scipy,zaxliu/scipy,aarchiba/scipy,jseabold/scipy,rmcgibbo/scipy,pnedunuri/scipy,aman-iitj/scipy,giorgiop/scipy,kleskjr/scipy,Newman101/scipy,hainm/scipy,Eric89GXL/scipy,mtrbean/scipy,mingwpy/scipy,FRidh/scipy,felipebetancur/scipy,ilayn/scipy,gfyoung/scipy,newemailjdm/scipy,larsmans/scipy,futurulus/scipy,ales-erjavec/scipy,newemailjdm/scipy,rgommers/scipy,Stefan-Endres/scipy,Eric89GXL/scipy,zxsted/scipy,perimosocordiae/scipy,richardotis/scipy,mortonjt/scipy,endolith/scipy,Dapid/scipy,lukauskas/scipy,bkendzior/scipy,jamestwebber/scipy,njwilson23/scipy,raoulbq/scipy,raoulbq/scipy,larsmans/scipy,zaxliu/scipy,Shaswat27/scipy,jjhelmus/scipy,rmcgibbo/scipy,Newman101/scipy,giorgiop/scipy,pschella/scipy,pyramania/scipy,jjhelmus/scipy,scipy/scipy,grlee77/scipy,cpaulik/scipy,anielsen001/scipy,fredrikw/scipy,bkendzior/scipy,newemailjdm/scipy,vhaasteren/scipy,pbrod/scipy,jsilter/scipy,Stefan-Endres/scipy,anielsen001/scipy,mingwpy/scipy,mgaitan/scipy,WillieMaddox/scipy,chatcannon/scipy,grlee77/scipy,giorgiop/scipy,pschella/scipy,pschella/scipy,andim/scipy,sriki18/scipy,tylerjereddy/scipy,gdooper/scipy,sonnyhu/scipy,sonnyhu/scipy,ndchorley/scipy,ChanderG/scipy,fernand/scipy,jseabold/scipy,matthewalbani/scipy,matthewalbani/scipy,ales-erjavec/scipy,Eric89GXL/scipy,jjhelmus/scipy,jamestwebber/scipy,chatcannon/scipy,pbrod/scipy,anntzer/scipy,kleskjr/scipy,jakevdp/scipy,nmayorov/scipy,witcxc/scipy,ortylp/scipy,andyfaff/scipy,minhlongdo/scipy,raoulbq/scipy,ilayn/scipy,zaxliu/scipy,ChanderG/scipy,richardotis/scipy,matthewalbani/scipy,matthewalbani/scipy,befelix/scipy,vigna/scipy,minhlongdo/scipy,argriffing/scipy,nvoron23/scipy,pizzathief/scipy,Srisai85/scipy,pizzathief/scipy,grlee77/scipy,maciejkula/scipy,pschella/scipy,argriffing/scipy,ChanderG/scipy,andim/scipy,mortada/scipy,ilayn/scipy,aarchiba/scipy,zerothi/scipy,Srisai85/scipy,vanpact/scipy,fredrikw/scipy,ilayn/scipy,jor-/scipy,nvoron23/scipy,befelix/scipy,lukauskas/scipy,nonhermitian/scipy,dch312/scipy,scipy/scipy,andyfaff/scipy,raoulbq/scipy,trankmichael/scipy,lukauskas/scipy,vigna/scipy,vberaudi/scipy,zaxliu/scipy,fredrikw/scipy,argriffing/scipy,vanpact/scipy,mikebenfield/scipy,pnedunuri/scipy,dch312/scipy,mtrbean/scipy,mikebenfield/scipy,gertingold/scipy,ChanderG/scipy,Shaswat27/scipy,fernand/scipy,jonycgn/scipy,kleskjr/scipy,Shaswat27/scipy,piyush0609/scipy,Dapid/scipy,haudren/scipy,vanpact/scipy,mdhaber/scipy,ales-erjavec/scipy,nvoron23/scipy,vberaudi/scipy,andyfaff/scipy,Kamp9/scipy,petebachant/scipy,nvoron23/scipy,lhilt/scipy,niknow/scipy,jsilter/scipy,vigna/scipy,sauliusl/scipy,arokem/scipy,Shaswat27/scipy,chatcannon/scipy,vhaasteren/scipy,pizzathief/scipy,mortada/scipy,FRidh/scipy,witcxc/scipy,gertingold/scipy,newemailjdm/scipy,anntzer/scipy,Stefan-Endres/scipy,Stefan-Endres/scipy,petebachant/scipy,larsmans/scipy,fernand/scipy,surhudm/scipy,mtrbean/scipy,trankmichael/scipy,jseabold/scipy,anntzer/scipy,piyush0609/scipy,apbard/scipy,arokem/scipy,gdooper/scipy,mdhaber/scipy,ndchorley/scipy,Gillu13/scipy,haudren/scipy,mortonjt/scipy,fredrikw/scipy,Kamp9/scipy,sonnyhu/scipy,jakevdp/scipy,zerothi/scipy,woodscn/scipy,tylerjereddy/scipy,sauliusl/scipy,endolith/scipy,aman-iitj/scipy,woodscn/scipy,endolith/scipy,cpaulik/scipy,efiring/scipy,gfyoung/scipy,gertingold/scipy,trankmichael/scipy,raoulbq/scipy,zxsted/scipy,mortada/scipy,pizzathief/scipy,maniteja123/scipy,behzadnouri/scipy,petebachant/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,jseabold/scipy,petebachant/scipy,befelix/scipy,niknow/scipy,aarchiba/scipy,mingwpy/scipy,efiring/scipy,jseabold/scipy,FRidh/scipy,bkendzior/scipy,gertin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