Auto merge of #27144 - semarie:openbsd-archive_format, r=alexcrichton
Auto merge of #27144 - semarie:openbsd-archive_format, r=alexcrichton

the "bsd" archive_format don't work under openbsd.
use of "" (system ar) is ok.
use of "gnu" is ok too.

r? @alexcrichton 

l0kod/rust,jroesch/rust,aidancully/rust,jroesch/rust,jroesch/rust,jashank/rust,l0kod/rust,zubron/rust,zubron/rust,pshc/rust,l0kod/rust,zubron/rust,jroesch/rust,zubron/rust,pshc/rust,aidancully/rust,zubron/rust,jashank/rust,vhbit/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,vhbit/rust,GBGamer/rust,jashank/rust,vhbit/rust,pshc/rust,dwillmer/rust,aidancully/rust,jashank/rust,vhbit/rust,zubron/rust,jroesch/rust,dwillmer/rust,l0kod/rust,dwillmer/rust,jroesch/rust,jroesch/rust,dwillmer/rust,jashank/rust,vhbit/rust,vhbit/rust,dwillmer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,pshc/rust,zubron/rust,jashank/rust,dwillmer/rust,GBGamer/rust,l0kod/rust,l0kod/rust,dwillmer/rust,pshc/rust,pshc/rust,pshc/rust,zubron/rust,graydon/rust,GBGamer/rust,dwillmer/rust,l0kod/rust,jashank/rust,GBGamer/rust,vhbit/rust,graydon/rust,jashank/rust,jroesch/rust,GBGamer/rust,l0kod/rust,graydon/rust,GBGamer/rust,pshc/rust,vhbit/rust