non_apple_gcc_version: support gcc5
non_apple_gcc_version: support gcc5

Closes Homebrew/homebrew#39899.

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

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