Teach brew to recognize gcc-HEAD as valid compiler
Teach brew to recognize gcc-HEAD as valid compiler

Building gcc with --HEAD results in most of the executables not having a
version suffix, e.g. Building/installing gcc 6 would result in gcc-6,
g++-6, etc. being installed, while building/installing gcc --HEAD would
result in gcc-, g++-, etc. being installed.

The lack of a version suffix prevented brew from recognizing a valid gcc
install, resulting in brew instructing users to install gcc before
building certain formulae even though gcc is installed.

A patch to the gcc formula makes the version number for --HEAD builds
the major version number of the stable version + 1 (7 at this time).
This patch teaches brew to recognize current --HEAD builds as valid
compilers.

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