Fix Gradle 9.3.0 compatibility: use exec() instead of project.exec() in doLast blocks

[Copilot]

Gradle 9.3.0 changed method resolution in task action contexts. Calling project.exec() within doLast now fails with Could not find method exec().

Changes

• Replace project.exec → exec in doLast closures (13 occurrences)
• Replace project.copy → copy for consistency (3 occurrences)

Files Modified

• linux/jdk/debian/build.gradle
• linux/jre/debian/build.gradle
• linux/ca-certificates/debian/build.gradle

Example

doLast {
    // Before (fails in Gradle 9.3.0)
    project.exec {
        commandLine "docker", "build", ...
    }
    
    // After (works in Gradle 9.3.0)
    exec {
        commandLine "docker", "build", ...
    }
}

These methods are directly available in the task action delegate and don't require the project. qualifier.

Original prompt

Fix the failing GitHub Actions workflow Check JDK on microsoft 11 Debian
Analyze the workflow logs, identify the root cause of the failure, and implement a fix.
Job ID: 61842409748
Job URL: https://github.com/adoptium/installer/actions/runs/21470727727/job/61842409748

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[karianna]

Another fix for #1325

[steelhead31]

Looks good.