Lo que es cierto es que el directorio del proyecto Solr está dentro del directorio padre de MyProject (pero no hay ningún módulo ni ninguna relación entre los 2, solo la conveniencia de FS). ¿Tengo que colocarlo?
$ mvn -DskipTests clean install
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for org.apache.lucene:lucene-solr-grandparent:pom:3.1-SNAPSHOT
[WARNING] 'parent.relativePath' points at com.mycompany:MyProject instead of org.apache:apache, please verify your project structure @ line 23, column 11
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
de pom.xml:
<parent>
<groupId>org.apache</groupId>
<artifactId>apache</artifactId>
<version>8</version>
</parent>
$ pwd
/Users/simpatico/ws/MyProjectBaseDir/solr