Launcher throws unclear error when starting in a JDK prior to 1.7

When starting the launcher with a Java version < 1.7 an exception is thrown:
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/onehippo/cms7/launcher/Launcher : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)

This is caused by the Launcher.java having a 1.7 specific diamond constructor, and the build does not enforce 1.6 compatibility.
Solution is to remove the diamond constructor and add to the launcher pom:

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<target>1.5</target>
<source>1.5</source>
</configuration>
</plugin>