Issue went away after putting "x86_64 armv7s arm64" in VALID_ARCHS for project in 12.4 (12D4e), this is contrary to some posts that suggest VALID_ARCHS should be empty. I went back to the old project and isolate which change I did when migrating the old project to 12.4 that exposed the permission error. The error message and logs are misleading.

Stuck with same issue after upgrading to XCode 12.4 and try to build an old project from prior versions