Build LuaRocks manifests on install
For backrgound see discussion here: https://github.com/sile-typesetter/sile/issues/2118
The bad effects of not running this can be seen in this test:
FROM docker.io/library/archlinux:base
RUN pacman --noconfirm -Syuq && yes | pacman -Sccq
RUN pacman --needed --noconfirm -S sile && yes | pacman -Sccq
RUN pacman --needed --noconfirm -S luarocks && yes | pacman -Sccq
# Note this list output will be blank in spite of having mane rocks installed
RUN luarocks --lua-version 5.1 list
RUN pacman --noconfirm -S lua51-cassowary && yes | pacman -Sccq
# This one will suddenly start showing output since the manifest rebulid got triggered
RUN luarocks --lua-version 5.1 list