Remove unnecessary --bind-ro for makepkg.conf.d in chroot.rs

[rmbruntz]

This block was added in 25ab260, 9 months ago, to fix #1156 (makepkg.conf.d/ not copied by arch-nspawn). The devtools package was updated 6 months ago to add support for this in archlinux/devtools@96eff02 and the 1.3.2 version with this feature was released on the same day. The two listed alternative providers for the devtools dependency (devtools-doas and devtools-git) have had this feature for the same timespan.

We can remove this band-aid and let arch-nspawn take care of both makepkg.conf and makepkg.conf.d/, which resolves the slight inconsistency (when one is modified during a chroot build) in the way these behave.

[Morganamilo]

It seems all the bind are unneeded and arch-nspawn mounts the cachedirs and repos. They can be removed too.

[NoiTheCat]

The most recent pacman update appears to break builds inside a chroot due to the --bind-ro option, so merging this may be very necessary for the next update.

This appears when attempting any kind of build:

(13/13) checking keys in keyring
(13/13) checking package integrity
(13/13) loading package files
(13/13) checking for file conflicts
(13/13) checking available disk space
error: Partition /etc/makepkg.conf.d is mounted read only
error: not enough free disk space
error: failed to commit transaction (not enough free disk space)
Errors occurred, no packages were upgraded.
error: failed to run: sudo arch-nspawn -C /tmp/.tmpAHNxT5 -M /etc/makepkg.conf /var/lib/paru/chroot/root --bind-ro /etc/makepkg.conf.d:/etc/makepkg.conf.d --bind-ro /var/lib/paru/repo --bind /var/cache/pacman/pkg/ --bind /var/lib/paru/repo pacman -Syu --noconfirm: 

Update: Can confirm on my end that removing --bind-ro fixes the issue.