Why can't the maven-deploy-plugin resolve my custom system property?

I'm using the gmaven-plugin to set a custom system property in my POM. This seems to work, as I'm able to successfully echo the property using the maven-antrun-plugin; however, the maven-deploy-plugin seems completely unaware of the property and is unable to resolve it.

Relevant portion of the POM:

<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.gmaven</groupId>
            <artifactId>gmaven-plugin</artifactId>
            <version>1.3</version>
            <executions>
                <execution>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>execute</goal>
                    </goals>
                    <configuration>
                        <source>
                            System.setProperty("nodotsversion", "${env.PATCH_VERSION}".replace('.', ''))
                        </source>
                    </configuration>
                </execution>
            </executions>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-antrun-plugin</artifactId>
            <version>1.6</version><!-- 1.2 in central -->
            <executions>
                <execution>
                    <id>compile</id>
                    <phase>compile</phase>
                    <configuration>
                        <target>
                            <echo message="${nodotsversion}" />     
                        </target>
                    </configuration>
                    <goals>
                        <goal>run</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-deploy-plugin</artifactId>
            <version>2.6</version>
            <goals>
                <goal>deploy-file</goal>
            </goals>
            <configuration>
                <repositoryId>artifactory</repositoryId>
                <packaging>sql</packaging>
                <generatePom>true</generatePom>
                <url>${project.distributionManagement.snapshotRepository.url}</url>
                <groupId>com.company.product</groupId>
                <artifactId>patch${nodotsversion}</artifactId>
                <version>1.0.0-SNAPSHOT</version>
                <file>${WORKSPACE}/myfile.sql</file>
            </configuration>
        </plugin>
    </plugins>
</build>

When I run this with mvn clean install deploy:deploy-file, I get the following error:

Caused by: org.apache.maven.plugin.MojoExecutionException: The artifact information is incomplete or not valid:
  [0]  'artifactId' with value 'patch${nodotsversion}' does not match a valid id pattern.

Why is the maven-antrun-plugin able to resolve my custom system property, while the maven-deploy-plugin is not?

I'm not sure, but I believe that the ${...} placeholder syntax can only resolve project properties. I believe the system properties are added to the project properties at a point in the build, which is why system properties are available in this way, but a system property added later in the build won't be available. You should add the property to the project properties instead.