AttachArtifact task fails with an error if used in external Ant build file:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.7:run (call-build) on project my-test-project: An Ant BuildException has occured: The following error occurred while executing this line:
[ERROR] C:\...\MyProject\build.xml:5: Maven project reference not found: maven.project
[ERROR] around Ant part ...<ant antfile="build.xml" target="mytarget"/>... @ 4:47 in C:\...\MyProject\target\antrun\build-main.xml
Setting inheritRefs="true" eliminates the error, but even then the artifact is not attached.