Fix Xcode 4.2 cc compiles
Fix Xcode 4.2 cc compiles

It seems like latest build of Xcode 4.2 doesn't create "-4.2" links in /usr/bin. Because of this recipes fail with "configure: error: C compiler cannot create executables" error.

Closes Homebrew/homebrew#7254.
Closes Homebrew/homebrew#7276.

Signed-off-by: Max Howell <max@methylblue.com>

Amended to work as intended, since /usr/bin/cc is actually since Xcode 4.

Amended commit message. First line must be less than 72 characters! :P
MikeMcQuaid/brew,tonyg/homebrew,gordonmcshane/homebrew,zmwangx/brew,mahori/brew,jmsundar/brew,jmsundar/brew,nandub/brew,EricFromCanada/brew,tonyg/homebrew,sjackman/homebrew,Homebrew/brew,alyssais/brew,mgrimes/brew,rwhogg/brew,sjackman/homebrew,gregory-nisbet/brew,mgrimes/brew,hanxue/linuxbrew,reitermarkus/brew,AnastasiaSulyagina/brew,DomT4/brew,gregory-nisbet/brew,pseudocody/brew,alyssais/brew,aw1621107/brew,rwhogg/brew,DomT4/brew,claui/brew,reelsense/brew,ilovezfs/brew,vitorgalvao/brew,vitorgalvao/brew,rwhogg/brew,vitorgalvao/brew,Homebrew/brew,aw1621107/brew,sjackman/homebrew,mistydemeo/homebrew,Linuxbrew/brew,nandub/brew,konqui/brew,nandub/brew,muellermartin/dist,tonyg/homebrew,MikeMcQuaid/brew,JCount/brew,amar-laksh/brew_sudo,mistydemeo/homebrew,staticfloat/brew,maxim-belkin/brew,Linuxbrew/brew,aw1621107/brew,amar-laksh/brew_sudo,jmsundar/brew,palxex/brew,bfontaine/brew,DomT4/brew,mahori/brew,amar-laksh/brew_sudo,EricFromCanada/brew,hanxue/linuxbrew,mgrimes/brew,MikeMcQuaid/brew,maxim-belkin/brew,reelsense/brew,Homebrew/brew,Homebrew/brew,hanxue/linuxbrew,Linuxbrew/brew,alyssais/brew,Linuxbrew/brew,vitorgalvao/brew,zmwangx/brew,JCount/brew,claui/brew,toonetown/homebrew,staticfloat/brew,claui/brew,toonetown/homebrew,maxim-belkin/brew,reitermarkus/brew,gregory-nisbet/brew,reelsense/brew,nandub/brew,ilovezfs/brew,konqui/brew,sjackman/homebrew,staticfloat/brew,mistydemeo/homebrew,toonetown/homebrew,reitermarkus/brew,pseudocody/brew,reitermarkus/brew,bfontaine/brew,AnastasiaSulyagina/brew,DomT4/brew,zmwangx/brew,EricFromCanada/brew,ilovezfs/brew,MikeMcQuaid/brew,konqui/brew,pseudocody/brew,palxex/brew,bfontaine/brew,muellermartin/dist,EricFromCanada/brew,mahori/brew,gordonmcshane/homebrew,JCount/brew,palxex/brew,muellermartin/dist,gordonmcshane/homebrew,AnastasiaSulyagina/brew,mahori/brew,claui/brew,konqui/brew,JCount/brew