antrun does not resolve build.xml from classpath

I am referencing an ant-file in the configuration of antrun-plugin.

 
<configuration>
  <target>
    <ant antfile="subscripts/build.xml">
      <target name="mytarget"/>
    </ant>
  </target>
</configuration>

The file "subscripts/build.xml" is included in the "src/main/resources" folder of a dependency of the antrun-plugin.

 
<dependency>
  <groupId>my.ant</groupId>
  <artifactId>subscripts</artifactId>
  <version>0.0.1-SNAPSHOT</version>
</dependency>

Layout of "my.ant.subscripts" is

 
src
 \main
   \resources
     \subscripts
       \build.xml

which is correctly packaged.

Given the basedir name "basedir", the antrun tells me on execution that the file "basedir/subscripts/build.xml" is not found.

My use-case includes about 30 projects, which execute the same ant target in their build lifecycle. I could solve the problem by putting a copy of "subscripts/build.xml" in every project's directory, but that is a very bad way.