`make bootstrap` doesn't work if `.config/emacs` is a submodule

Using Borg version: ``` main origin/main 74a930900728a43c32f3356ae21b3da36af375cc Author: Jonas Bernoulli <jonas@bernoul.li> AuthorDate: Mon, 18 Dec 2023 12:19:02 -0800 Commit: Jonas Bernoulli <jonas@bernoul.li> CommitDate: Mon, 18 Dec 2023 14:57:00 -0800 ``` If `.config/emacs` is a submodule, then its `.config/emacs/.git` is actually a pointer into the parent repo's `.git/modules`. `make bootstrap` tries to clone drones into `.config/emacs.git/lib/blah` which doesn't work since `.config/emacs/.git` is a "pointer" file. e.g. ``` --- [lib/git-timemachine] --- Cloning lib/git-timemachine from origin (https://codeberg.org/pidu/git-timemachine) Cloning into 'lib/git-timemachine'... fatal: Invalid path '/home/me/.config/emacs/.git/modules': Not a directory Cloning failed ``` and `/home/me/.config/emacs/.git` contains ``` gitdir: ../../.git/modules/.config/emacs ```