Define a dummy SCM and then use buildNumber item to get sequential build number instead of value defined by revisionOnScmFailure property.
pom.xml:
<project ...>
<scm>
<connection>scm:svn:http://127.0.0.1/dummy</connection>
<developerConnection>scm:svn:https://127.0.0.1/dummy</developerConnection>
<tag>HEAD</tag>
<url>http://127.0.0.1/dummy</url>
</scm>
<build>
<plugins>
...
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>buildnumber-maven-plugin</artifactId>
<version>1.1</version>
<executions>
<execution>
<id>buildnumber</id>
<phase>validate</phase>
<goals>
<goal>create</goal>
</goals>
</execution>
</executions>
<configuration>
<format>{0,number}</format>
<items>
<item>buildNumber</item>
</items>
<doCheck>false</doCheck>
<doUpdate>false</doUpdate>
<revisionOnScmFailure>unknownbuild</revisionOnScmFailure>
</configuration>
</plugin>
</plugins>
</build>
</project>