cmd/update: make `curl` respect `HOMEBREW_CURLRC`
cmd/update: make `curl` respect `HOMEBREW_CURLRC`

claui/brew,maxim-belkin/brew,nandub/brew,MikeMcQuaid/brew,sjackman/homebrew,Homebrew/brew,mahori/brew,MikeMcQuaid/brew,reitermarkus/brew,vitorgalvao/brew,JCount/brew,Linuxbrew/brew,JCount/brew,EricFromCanada/brew,konqui/brew,EricFromCanada/brew,sjackman/homebrew,nandub/brew,reitermarkus/brew,EricFromCanada/brew,Homebrew/brew,Linuxbrew/brew,JCount/brew,mahori/brew,Homebrew/brew,reitermarkus/brew,maxim-belkin/brew,konqui/brew,MikeMcQuaid/brew,vitorgalvao/brew,JCount/brew,nandub/brew,Linuxbrew/brew,maxim-belkin/brew,Homebrew/brew,mahori/brew,sjackman/homebrew,vitorgalvao/brew,mahori/brew,claui/brew,claui/brew,konqui/brew,nandub/brew,EricFromCanada/brew,vitorgalvao/brew,MikeMcQuaid/brew,claui/brew,konqui/brew,reitermarkus/brew,Linuxbrew/brew,sjackman/homebrew