devel: reset mirrors when building devel
devel: reset mirrors when building devel

Otherwise stable mirrors will be considered when the devel download
fails.

Fixes Homebrew/homebrew#9910.

reelsense/brew,alyssais/brew,sjackman/homebrew,mahori/brew,claui/brew,zmwangx/brew,DomT4/brew,hanxue/linuxbrew,vitorgalvao/brew,DomT4/brew,reitermarkus/brew,hanxue/linuxbrew,Linuxbrew/brew,jmsundar/brew,amar-laksh/brew_sudo,DomT4/brew,mahori/brew,konqui/brew,gregory-nisbet/brew,jmsundar/brew,muellermartin/dist,rwhogg/brew,gregory-nisbet/brew,EricFromCanada/brew,staticfloat/brew,JCount/brew,MikeMcQuaid/brew,mistydemeo/homebrew,mistydemeo/homebrew,pseudocody/brew,sjackman/homebrew,maxim-belkin/brew,palxex/brew,nandub/brew,aw1621107/brew,mgrimes/brew,EricFromCanada/brew,konqui/brew,vitorgalvao/brew,reitermarkus/brew,mahori/brew,nandub/brew,reelsense/brew,zmwangx/brew,pseudocody/brew,alyssais/brew,AnastasiaSulyagina/brew,ilovezfs/brew,ilovezfs/brew,bfontaine/brew,bfontaine/brew,tonyg/homebrew,gordonmcshane/homebrew,mgrimes/brew,mahori/brew,MikeMcQuaid/brew,JCount/brew,sjackman/homebrew,konqui/brew,hanxue/linuxbrew,Homebrew/brew,AnastasiaSulyagina/brew,nandub/brew,alyssais/brew,maxim-belkin/brew,reitermarkus/brew,vitorgalvao/brew,Homebrew/brew,muellermartin/dist,Linuxbrew/brew,gordonmcshane/homebrew,gregory-nisbet/brew,konqui/brew,amar-laksh/brew_sudo,sjackman/homebrew,staticfloat/brew,claui/brew,aw1621107/brew,MikeMcQuaid/brew,muellermartin/dist,claui/brew,palxex/brew,ilovezfs/brew,pseudocody/brew,tonyg/homebrew,rwhogg/brew,toonetown/homebrew,claui/brew,EricFromCanada/brew,maxim-belkin/brew,MikeMcQuaid/brew,EricFromCanada/brew,mistydemeo/homebrew,tonyg/homebrew,reitermarkus/brew,palxex/brew,Homebrew/brew,bfontaine/brew,JCount/brew,Linuxbrew/brew,nandub/brew,vitorgalvao/brew,amar-laksh/brew_sudo,toonetown/homebrew,toonetown/homebrew,staticfloat/brew,gordonmcshane/homebrew,mgrimes/brew,JCount/brew,aw1621107/brew,jmsundar/brew,Homebrew/brew,zmwangx/brew,rwhogg/brew,reelsense/brew,DomT4/brew,Linuxbrew/brew,AnastasiaSulyagina/brew