The current JBT/maven 3.3.x builds fail due to an incompatibility between m2e-core and m2eclipse-wtp.
The Sonatype Hudson grid, used to build m2eclipse-wtp, is down, for good.
Seems the best way to build m2eclipse-wtp is to do it on our own infrastructure.
Ideally we'd need to create 2 new Hudson jobs on the JBoss grid, building https://github.com/sonatype/m2eclipse-wtp.git
and basically running

 mvn clean deploy -Dtarget.platform=m2e-wtp-e36 -Ppublish-site

and

 mvn clean deploy -Dtarget.platform=m2e-wtp-e37

We'll need to set the appropriate parameters for site publishing (see https://github.com/sonatype/m2eclipse-wtp/blob/master/org.maven.ide.eclipse.wtp.feature/pom.xml#L83) as well as things like -Xmx512m and the path to a private local repo, if needed.

Please contact me you need more informations.