allow installation of formulae from the current folder
allow installation of formulae from the current folder

Closes Homebrew/homebrew#19177.

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