I just updated to Xcode 12.0.1 from AppStore opened my old project and after build got an error.
as I research on SO for a solution some answered mentioned changing architecture in the build setting and changing build active architecture only setting. so I did but that didn't help.
here the picture of the build setting architecture section:
as I mentioned I have gone through the same so question but they didn't help for that I have uploaded a screenshot of the solution I used.
Just clean the build folder and build project. Doing this my issue is solved.
Or You can add armv7 to the Build Settings -> Architectures -> Excluded Architectures. This might solve the issue for some.