ENV.rb: Set flags for Objective-C
ENV.rb: Set flags for Objective-C

We set defaults for C and C++, might as well do the same for Objective-C and
Objective-C++.

Closes Homebrew/homebrew#10354.

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