Remove HOMEBREW_CC warning from ENV.compiler
Remove HOMEBREW_CC warning from ENV.compiler

ENV.compiler is called outside setting up the build environment, where
values unsupported for user input might have been specified - for
example, GNU GCC executables.

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