[SOLVED] Maven not running generate goal during Maven build or Maven generate-sources from within Eclipse

I'm new to Maven and cannot seem to get a generate goal to run. I'm using Maven from within Eclipse.

Here is the POM.XML:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.mbm</groupId>
    <artifactId>properties</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Properties</name>
    <description>Define and process program arguments</description>
    <dependencies>
    </dependencies>
    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.codehaus.mojo</groupId>
                    <artifactId>sablecc-maven-plugin</artifactId>
                    <version>2.4-SNAPSHOT</version>
                    <configuration>
                        <sourceDirectory>${basedir}/src/main/java/com/mbm/properties/grammar</sourceDirectory>
                        <outputDirectory>${basedir}/src/main/gen-java/com/mbm/properties/sablecc</outputDirectory>
                    </configuration>
                    <executions>
                        <execution>
                            <goals>
                                <goal>generate</goal>
                            </goals>
                        </execution>
                    </executions>
                </plugin>
            </plugins>
        </pluginManagement>
        <plugins>
        </plugins>
    </build>
</project>

I want the sablecc-maven-plugin to run. This plugin invokes SableCC, which is YAPG (yet another parser generator), that reads in a grammar file and generates source code in the directories specified within the <configuration> element. It appears that the plugin never ran. After doing a Maven generate-sources from Exclipse, the SableCC generated source files were still very old (from 2018), so I know SableCC didn't run. Also, there's nothing in Maven debug output indicating it even attempted to run the plugin. Here is that output:

Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: C:\Users\mbmas_000\workspace\Properties\EMBEDDED
Java version: 1.8.0_221, vendor: Oracle Corporation, runtime: C:\Program Files\Java\jdk1.8.0_221\jre
Default locale: en_US, platform encoding: Cp1252
OS name: "windows 10", version: "10.0", arch: "amd64", family: "windows"
[DEBUG] Created new class realm maven.api
[DEBUG] Importing foreign packages into class realm maven.api
[DEBUG]   Imported: javax.annotation.* < plexus.core
[DEBUG]   Imported: javax.annotation.security.* < plexus.core
[DEBUG]   Imported: javax.enterprise.inject.* < plexus.core
[DEBUG]   Imported: javax.enterprise.util.* < plexus.core
[DEBUG]   Imported: javax.inject.* < plexus.core
[DEBUG]   Imported: org.apache.maven.* < plexus.core
[DEBUG]   Imported: org.apache.maven.artifact < plexus.core
[DEBUG]   Imported: org.apache.maven.classrealm < plexus.core
[DEBUG]   Imported: org.apache.maven.cli < plexus.core
[DEBUG]   Imported: org.apache.maven.configuration < plexus.core
[DEBUG]   Imported: org.apache.maven.exception < plexus.core
[DEBUG]   Imported: org.apache.maven.execution < plexus.core
[DEBUG]   Imported: org.apache.maven.execution.scope < plexus.core
[DEBUG]   Imported: org.apache.maven.lifecycle < plexus.core
[DEBUG]   Imported: org.apache.maven.model < plexus.core
[DEBUG]   Imported: org.apache.maven.monitor < plexus.core
[DEBUG]   Imported: org.apache.maven.plugin < plexus.core
[DEBUG]   Imported: org.apache.maven.profiles < plexus.core
[DEBUG]   Imported: org.apache.maven.project < plexus.core
[DEBUG]   Imported: org.apache.maven.reporting < plexus.core
[DEBUG]   Imported: org.apache.maven.repository < plexus.core
[DEBUG]   Imported: org.apache.maven.rtinfo < plexus.core
[DEBUG]   Imported: org.apache.maven.settings < plexus.core
[DEBUG]   Imported: org.apache.maven.toolchain < plexus.core
[DEBUG]   Imported: org.apache.maven.usability < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.* < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.authentication < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.authorization < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.events < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.observers < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.proxy < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.repository < plexus.core
[DEBUG]   Imported: org.apache.maven.wagon.resource < plexus.core
[DEBUG]   Imported: org.codehaus.classworlds < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.* < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.classworlds < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.component < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.configuration < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.container < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.context < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.lifecycle < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.logging < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.personality < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.util.xml.Xpp3Dom < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.util.xml.pull.XmlPullParser < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.util.xml.pull.XmlPullParserException < plexus.core
[DEBUG]   Imported: org.codehaus.plexus.util.xml.pull.XmlSerializer < plexus.core
[DEBUG]   Imported: org.eclipse.aether.* < plexus.core
[DEBUG]   Imported: org.eclipse.aether.artifact < plexus.core
[DEBUG]   Imported: org.eclipse.aether.collection < plexus.core
[DEBUG]   Imported: org.eclipse.aether.deployment < plexus.core
[DEBUG]   Imported: org.eclipse.aether.graph < plexus.core
[DEBUG]   Imported: org.eclipse.aether.impl < plexus.core
[DEBUG]   Imported: org.eclipse.aether.installation < plexus.core
[DEBUG]   Imported: org.eclipse.aether.internal.impl < plexus.core
[DEBUG]   Imported: org.eclipse.aether.metadata < plexus.core
[DEBUG]   Imported: org.eclipse.aether.repository < plexus.core
[DEBUG]   Imported: org.eclipse.aether.resolution < plexus.core
[DEBUG]   Imported: org.eclipse.aether.spi < plexus.core
[DEBUG]   Imported: org.eclipse.aether.transfer < plexus.core
[DEBUG]   Imported: org.eclipse.aether.version < plexus.core
[DEBUG]   Imported: org.fusesource.jansi.* < plexus.core
[DEBUG]   Imported: org.slf4j.* < plexus.core
[DEBUG]   Imported: org.slf4j.event.* < plexus.core
[DEBUG]   Imported: org.slf4j.helpers.* < plexus.core
[DEBUG]   Imported: org.slf4j.spi.* < plexus.core
[DEBUG] Populating class realm maven.api
[INFO] Error stacktraces are turned on.
[DEBUG] Message scheme: plain
[DEBUG] Reading global settings from settings.xml
[DEBUG] Reading user settings from C:\Users\mbmas_000\.m2\settings.xml
[DEBUG] Reading global toolchains from toolchains.xml
[DEBUG] Reading user toolchains from C:\Users\mbmas_000\.m2\toolchains.xml
[DEBUG] Using local repository at C:\Users\mbmas_000\.m2\repository
[DEBUG] Using manager EnhancedLocalRepositoryManager with priority 10.0 for C:\Users\mbmas_000\.m2\repository
[INFO] Scanning for projects...
[DEBUG] Extension realms for project com.mbm:properties:jar:0.0.1-SNAPSHOT: (none)
[DEBUG] Looking up lifecycle mappings for packaging jar from ClassRealm[plexus.core, parent: null]
[DEBUG] === REACTOR BUILD PLAN ================================================
[DEBUG] Project: com.mbm:properties:jar:0.0.1-SNAPSHOT
[DEBUG] Tasks:   [generate-sources]
[DEBUG] Style:   Regular
[DEBUG] =======================================================================
[INFO] 
[INFO] -------------------------< com.mbm:properties >-------------------------
[INFO] Building Properties 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[DEBUG] Lifecycle default -> [validate, initialize, generate-sources, process-sources, generate-resources, process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy]
[DEBUG] Lifecycle clean -> [pre-clean, clean, post-clean]
[DEBUG] Lifecycle site -> [pre-site, site, post-site, site-deploy]
[DEBUG] === PROJECT BUILD PLAN ================================================
[DEBUG] Project:       com.mbm:properties:0.0.1-SNAPSHOT
[DEBUG] Dependencies (collect): []
[DEBUG] Dependencies (resolve): []
[DEBUG] Repositories (dependencies): [redhat-ga-repository (http://maven.repository.redhat.com/ga/, default, releases), central (https://repo.maven.apache.org/maven2, default, releases)]
[DEBUG] Repositories (plugins)     : [redhat-ga-repository (http://maven.repository.redhat.com/ga/, default, releases), central (https://repo.maven.apache.org/maven2, default, releases)]
[DEBUG] =======================================================================
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.153 s
[INFO] Finished at: 2020-05-04T10:58:08-07:00
[INFO] ------------------------------------------------------------------------

What am I doing wrong?