Setup

Make sure your \(\TeX\) installation is functional. Refer to Prerequisites section of AUCTeX manual

Assimilate auctex:

M-x borg-assimilate <RET> auctex <RET>

Ignore the compilation errors for now. Update .gitmodules:

[submodule "auctex"]
	path = lib/auctex
	url = [email protected]:emacsmirror/auctex.git
	load-path = .
	build-step = ./autogen.sh
	build-step = ./configure --with-lispdir=~/.emacs.d/lib/auctex
	build-step = make
	build-step = make doc
	build-step = borg-maketexi
	build-step = borg-makeinfo
	build-step = borg-update-autoloads

Now build AUCTeX again:

M-x borg-build <RET> auctex <RET>

We are done, initialization should now be normal:

(use-package tex-site
  :load-path "lib/auctex/")

John Wiegly has detailed configuration if you want something advanced.

Why?

Borg executes default build steps using the lisp functions borg-update-autoloads, borg-compile, borg-maketexi, and borg-makeinfo.

But building AUCTeX requires a few extra steps to build, which we add to .gitmodules. For details check submodule.DRONE.build-step variable in the manual.

If something does not work for you, send me an email or visit the IRC channel.