I had a similar error in my project (also running Xcode 13.2.1 on an M1 mini), but only in the unit test target associated with my program (a command line tool rather than an application). Oddly, the error pointed to the
@testable import <program_name> line in one of my unit test source files, and only when the selected scheme was the one for the unit test target.
Searching the Internet for the text of the error message led me to a Developer Forum post that suggested editing the Architecture setting (under Build Settings) and replace the default value of "$(ARCHS_STANDARD)" (displayed as "Standard Architectures (Apple Silicon, Intel)") with the explicit values "arm64" and "x86_64". I tried this and it seemed to work for me.
However, in subsequent experimentation I found that it appeared to be sufficient (in my case, anyway) to ensure that the Architecture was set to "$(ARCHS_STANDARD)" directly on the project, instead of inheriting the value from the "macOS Default". So your mileage may vary.
In any case, I hope this helps.