Unlink before rewriting link
Unlink before rewriting link

ln_sf does the right thing when `dest` is a symlink pointing to a file:
the symlink gets overwritten with a link pointing to the new src. But
when dest points to a directory, we create a new symlink inside the
folder dest points to, which doesn't help us at all.

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