Return value of File.delete() ignored in EarMojo

## Description

In `EarMojo.java:881`, the return value of `File.delete()` is ignored:

```java
resourceFile.delete();
```

If the file cannot be deleted (e.g., locked by another process, permission denied), the failure goes undetected. In incremental builds, stale resources can remain behind.

## Expected behavior

Check the return value and log a warning:

```java
if (!resourceFile.delete()) {
getLog().warn("Failed to delete outdated resource: " + resourceFile);
}
```

Start in EarMojo.java at line 881, where resourceFile.delete() is called, and inspect the surrounding incremental-build cleanup flow. Done means a failed deletion is detected and logged as a warning while successful deletions retain their current behavior.

Written by the indexing model from the issue text.