Default to LLVM on Snow Leopard
Default to LLVM on Snow Leopard

On Leopard you can enable it by defining the environment variable:

    HOMEBREW_USE_LLVM

I didn't enable it on Leopard by default because it doesn't get as much testing, and I don't want to rock the boat. On Snow Leopard people are forigiving of issues because it is new and many compiles fail anyway. And if you installed Snow Leopard you *want* the cutting edge.

Closes Homebrew/homebrew#29

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