In the Build and Run options, enable "Save all files before build", "Always build project before deploying it", and "Always deploy project before running it".

Steps to reproduce:
1. Make a change to a read-only file.
2. Press Ctrl + B to build, or Ctrl + R to run the project.
3. You are prompted for how to save the file, press Cancel.
PROBLEM: The project is still built and ran.

This feature was added in (I think) 2.2, but no longer works in 2.4.