CircleCI: add layer2 cache of newly added coreboot git forks to speedup builds from cache#1555

tlaurion wants to merge 2 commits intolinuxboot:masterlinuxboot/heads:masterfrom

tlaurion:circleci-add_layer2_coreboot_build_Cache_for_forkstlaurion/heads:circleci-add_layer2_coreboot_build_Cache_for_forksCopy head branch name to clipboard