Solution 1: Use Multiple Targets
1. Create a new target for each file with a main() function:
   Go to the File menu, select New, then Target.
   Choose a C executable template.
   Name the target (e.g., Program1, Program2).

2. Add the desired file to the new target:
   In the file inspector on the right, ensure the correct target is checked 
   for each file.
3. Build and run the target you want:
   Select the desired target from the dropdown menu in the toolbar.
   Press Run.

This keeps each main() function in its own target, avoiding conflicts.

Read more about the solution here: https://impetusorgansseparation.com/avnneqwn?key=670ae0c3b093d8e8ac42c57aa7da8c14