Auto merge of #26213 - semarie:openbsd-morestack, r=alexcrichton
Auto merge of #26213 - semarie:openbsd-morestack, r=alexcrichton

don't try to bind __morestack symbol under OpenBSD as the platform don't
have morestack support.

r? @alexcrichton 

it unbreak build under OpenBSD. Does some others platforms don't have morestack too ? They should be impacted by this problem too.

graydon/rust,robertg/rust,KokaKiwi/rust,vhbit/rust,GBGamer/rust,l0kod/rust,nwin/rust,GBGamer/rust,jroesch/rust,zubron/rust,reem/rust,jashank/rust,jashank/rust,mvdnes/rust,reem/rust,pelmers/rust,dwillmer/rust,jashank/rust,nwin/rust,omasanori/rust,reem/rust,graydon/rust,jroesch/rust,aidancully/rust,nwin/rust,graydon/rust,vhbit/rust,vhbit/rust,graydon/rust,robertg/rust,l0kod/rust,pshc/rust,dwillmer/rust,zubron/rust,aidancully/rust,pelmers/rust,dwillmer/rust,jroesch/rust,jashank/rust,l0kod/rust,nwin/rust,KokaKiwi/rust,reem/rust,pelmers/rust,KokaKiwi/rust,dwillmer/rust,zubron/rust,aidancully/rust,nwin/rust,omasanori/rust,mvdnes/rust,pelmers/rust,robertg/rust,pshc/rust,l0kod/rust,GBGamer/rust,dwillmer/rust,pshc/rust,reem/rust,jroesch/rust,zubron/rust,robertg/rust,dwillmer/rust,nwin/rust,vhbit/rust,dwillmer/rust,KokaKiwi/rust,pelmers/rust,mvdnes/rust,jroesch/rust,graydon/rust,mvdnes/rust,jashank/rust,GBGamer/rust,aidancully/rust,omasanori/rust,pshc/rust,graydon/rust,KokaKiwi/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,jroesch/rust,vhbit/rust,dwillmer/rust,jashank/rust,pshc/rust,zubron/rust,mvdnes/rust,vhbit/rust,aidancully/rust,omasanori/rust,pshc/rust,l0kod/rust,nwin/rust,jroesch/rust,zubron/rust,mvdnes/rust,reem/rust,omasanori/rust,pelmers/rust,vhbit/rust,nwin/rust,l0kod/rust,robertg/rust,GBGamer/rust,pshc/rust,GBGamer/rust,KokaKiwi/rust,omasanori/rust,jashank/rust,vhbit/rust,l0kod/rust,l0kod/rust,zubron/rust,jashank/rust,robertg/rust,zubron/rust,jroesch/rust,pshc/rust