update: make GIT_EXECUTABLE an absolute path.
update: make GIT_EXECUTABLE an absolute path.

Otherwise it can end up as e.g. `bin/git` which then breaks when we
`cd` to another directory and try to run it.

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