tar: file changed as we read it

[bcressey]

I've noticed occasional build failures with VMware variants because of errors like this:

tar: bottlerocket-vmware-k8s-1.31-x86_64-1.34.0-f3d88ccc6.vmdk: file changed as we read it

I'm pretty sure this happens if we get a sequence like this:

1. rpm2img, rpm2kmodkit, rpm2migrations all start
2. rpm2img creates the VMDK file
3. rpm2kmodkit or rpm2migrations finishes
4. rpm2img starts the OVA creation
5. the recursive chown of everything in /output starts
6. rpm2img observes the VMDK change from root:root to builder:builder - error!

In theory any of these stages could finish first, then disrupt a tar operation in progress in one of the other stages when it runs chown.