bottle: only set prefix if un-relocatable
bottle: only set prefix if un-relocatable

Closes Homebrew/homebrew#43819.

Signed-off-by: Xu Cheng <9a05244150b861e40c78843b801eed71bca54eac@me.com>

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