build-helper-maven-plugin on profile doesn't work

[provide a description of the issue]

Dear support,
I am trying to use the profiles in a POM to add extra source directory.
I am using a plugin which generate java code in a custom directory target/generated-sources/plc4x and for telling VSC that this directory has sono code I would like to use build-helper-maven-plugin.

If I use the plugin inside the POM it works:

  <build>
    <plugins>
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <executions>
          <execution>
            <id>add-source</id>
            <phase>generate-sources</phase>
            <goals>
              <goal>add-source</goal>
            </goals>
            <configuration>
              <sources>
                <source>target/generated-sources/plc4x</source>
              </sources>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

In this way VSC add correctly the new directory in the .classpath file:

        <classpathentry kind="src" output="target/classes" path="target/generated-sources/plc4x">
                <attributes>
                        <attribute name="optional" value="true"/>
                        <attribute name="maven.pomderived" value="true"/>
                </attributes>
        </classpathentry>

but if I try to use profiles to handle the plugin just in some circumstances, it doesn't work:

<profiles>
<profile>
      <id>vsc</id>
      <activation>
        <os>
          <family>mac</family>
        </os>
      </activation>
            <build>
        <pluginManagement>
          <plugins>
            <plugin>
              <groupId>org.codehaus.mojo</groupId>
              <artifactId>build-helper-maven-plugin</artifactId>
              <executions>
                <execution>
                  <id>add-source</id>
                  <phase>generate-sources</phase>
                  <goals>
                    <goal>add-source</goal>
                  </goals>
                  <configuration>
                    <sources>
                      <source>target/generated-sources/plc4x</source>
                    </sources>
                  </configuration>
                </execution>
              </executions>
            </plugin>
          </plugins>
        </pluginManagement>
      </build>
</profile>
</profiles>

In this way the entry in the .classpath file is not present.

Environment

• Operating System: Mac Os 11.2
• JDK version: openjdk version "13.0.2" 2020-01-14
• Visual Studio Code version: 1.53.0

Current Result

I can't use profiles to handle the build-helper-maven-plugin

Expected Result

To have the the path entry in the classpath in both the situation

Regards,
Stefano Bossi

Reproduziere die beiden POM-Konfigurationen unter macOS mit den aufgeführten JDK- und VS Code-Versionen und vergleiche den generierten .classpath-Eintrag, wenn sich build-helper-maven-plugin unter build beziehungsweise in einem OS-aktivierten Profil befindet. Beginne mit der Maven-Profilbehandlung und dem Import von Java-Projekten in VS Code; als abgeschlossen gilt die Aufgabe, wenn der Pfad zu den generierten Quellen in .classpath in beiden beschriebenen Situationen erscheint.