podman: rootless: permission denied when trying to write to /run/user

/kind bug

Description When running podman from an unprivileged user (uid=1001(tobwen) gid=1001(tobwen) groups=1001(tobwen)), podman tried to write to /run/user, where the user doesn’t have permission on Debian.

Steps to reproduce the issue:

1. no podman-config file exists (I’m using switches only)
2. all the dependencies (crun etc.) are installed and the paths are correct

/home/tobwen/podman/usr/local/bin/podman \
--conmon /home/tobwen/podman/usr/local/bin/conmon \
--network-cmd-path /home/tobwen/podman/usr/local/bin/slirp4netns \
--runtime /home/tobwen/podman/usr/local/bin/crun \
--storage-driver overlay \
--storage-opt 'overlay.mount_program=/home/tobwen/podman/usr/local/bin/fuse-overlayfs'

Describe the results you received:

ERRO[0000] could not get runtime: error generating default config from memory: cannot mkdir /run/user/0/libpod: mkdir /run/user/0/libpod: permission denied

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

Error: could not get runtime: error generating default config from memory: cannot mkdir /run/user/0/libpod: mkdir /run/user/0/libpod: permission denied

Output of podman info --debug:

Error: could not get runtime: error generating default config from memory: cannot mkdir /run/user/0/libpod: mkdir /run/user/0/libpod: permission denied

Package info (e.g. output of rpm -q podman or apt list podman):

built from source with a stack, which worked in the past

Additional environment details (AWS, VirtualBox, physical, etc.): Debian 10 on Virtual Box 6 on Windows 10 (all 64-bit)