Description:

LVM utilities need access the sockets in /run/lvm, otherwise it falls back to device scan.
It was not be a problem before. But recently due to some upsteam changes, they will try udev and wait for 10 seconds for each device. This can make grub-mkconfig stuck for tens of minutes.

Despite upstream, it seems easier and more elegant to fix this in arch-chroot script by providing /run/lvm access to chroot environment. Like bind-mounting into the new root, and add a symbolic link at /run/lvm.

Additional info:

[root@archiso /]# time vgs
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
WARNING: Device /dev/loop0 not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/sda not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/vg0/swap not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/sda1 not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/vg0/root not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/sda2 not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/loop0 not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/vg0/swap not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/sda1 not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/vg0/root not initialized in udev database even after waiting 10000000 microseconds.
WARNING: Device /dev/sda2 not initialized in udev database even after waiting 10000000 microseconds.
VG #PV #LV #SN Attr VSize VFree
vg0 1 2 0 wz--n- 15.53g 0

real 1m50.289s
user 0m0.047s
sys 0m0.081s

Steps to reproduce:
Follow installation wiki, setup root using lvm, install grub and run grub-mkconfig.
Or just run LVM utils after chroot.