title: How do I skip a Maven plugin execution if "-DskipTests" or "-Dmaven.test.skip=true" is specified?
body: <p>I'm using Maven 3.0.3.  I have this plugin, which normally I want to run before my JUnit tests are executed:</p>
  
  <pre class="lang-xml prettyprint-override"><code>    &lt;profile&gt;
          &lt;id&gt;dev&lt;/id&gt;
          &lt;activation&gt;
              &lt;activeByDefault&gt;true&lt;/activeByDefault&gt;
          &lt;/activation&gt;
          &lt;properties&gt;
              &lt;test.mysql.db.user&gt;sbjunituser&lt;/test.mysql.db.user&gt;
              &lt;test.mysql.db.password&gt;&lt;/test.mysql.db.password&gt;
              &lt;test.mysql.db.prefix&gt;sbjunit&lt;/test.mysql.db.prefix&gt;
              &lt;test.mysql.db.sid&gt;${test.mysql.db.prefix}_${project.artifactId}&lt;/test.mysql.db.sid&gt;
              &lt;test.mysql.db.host&gt;localhost&lt;/test.mysql.db.host&gt;
              &lt;test.mysql.db.port&gt;3306&lt;/test.mysql.db.port&gt;
              &lt;test.mysql.dataSource.url&gt;jdbc:mysql://${test.mysql.db.host}:${test.mysql.db.port}/${test.mysql.db.sid}&lt;/test.mysql.dataSource.url&gt;
              &lt;test.mysql.dataSource.driverClassName&gt;com.mysql.jdbc.Driver&lt;/test.mysql.dataSource.driverClassName&gt;
          &lt;/properties&gt;
          &lt;build&gt;
              &lt;plugins&gt;
          &lt;!--  Run the liquibase scripts --&gt;
          &lt;plugin&gt;
              &lt;groupId&gt;org.liquibase&lt;/groupId&gt;
              &lt;artifactId&gt;liquibase-maven-plugin&lt;/artifactId&gt;
              &lt;version&gt;2.0.1&lt;/version&gt;
              &lt;dependencies&gt;
                  &lt;dependency&gt;
                      &lt;groupId&gt;mysql&lt;/groupId&gt;
                      &lt;artifactId&gt;mysql-connector-java&lt;/artifactId&gt;
                      &lt;version&gt;5.1.18&lt;/version&gt;
                  &lt;/dependency&gt;
              &lt;/dependencies&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;build-database&lt;/id&gt;
                      &lt;phase&gt;process-test-classes&lt;/phase&gt;
                      &lt;configuration&gt;
                          &lt;driver&gt;com.mysql.jdbc.Driver&lt;/driver&gt;
                          &lt;url&gt;jdbc:mysql://${test.mysql.db.host}:${test.mysql.db.port}/${test.mysql.db.sid}&lt;/url&gt;
                          &lt;username&gt;${test.mysql.db.user}&lt;/username&gt;
                          &lt;password&gt;${test.mysql.db.password}&lt;/password&gt;
                          &lt;changeLogFile&gt;${project.build.directory}/db.changelog-master.xml&lt;/changeLogFile&gt;
                          &lt;promptOnNonLocalDatabase&gt;false&lt;/promptOnNonLocalDatabase&gt;
                      &lt;/configuration&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;update&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
  </code></pre>
  
  <p>However, if someone specifies <code>-Dmaven.test.skip=true</code> or <code>-DskipTests</code>, I would like to skip this plugin from running.  How do I do that?  I tried changing the execution phase to "test", but then my unit tests get run before this plugin, which is not what I want.</p>