An existing B4A project was transferred to the new B4X structure (B4A/B4i/B4J) and could be successfully installed and used with B4i (version 6.80) in debug mode on a real device via Hosted Builder.
When trying to create a release version the following message appears:
Building Xcode project Error,
Access to the path 'D:\xyz\myprojectxy\B4i\Objects\src\sy_hahicon0.png' is denied.
If the file definitely exists then the usual reason for this is that another process has the file open. Try logging out of Windows and logging in again, this will kill all your existing processes - much the same as a reboot but less drastic.
Based on the hints from agraham and erel, paying attention to the files involved helped.
For all files in the Files folder, I made certain that readonly was off.
Then I cleaned the project, manually deleted the \src folder and restarted B4i.