circle.yml: Fix unshallow error for Linuxbrew
circle.yml: Fix unshallow error for Linuxbrew

Fix fatal: --unshallow on a complete repository does not make sense

maxim-belkin/brew,maxim-belkin/brew,rwhogg/brew,hanxue/linuxbrew,Linuxbrew/brew,maxim-belkin/brew,hanxue/linuxbrew,rwhogg/brew,Linuxbrew/brew,Linuxbrew/brew,hanxue/linuxbrew,rwhogg/brew,Linuxbrew/brew