First build the UI project from git@github.com:Mgiepz/saiku-adhoc-ui.git by checking it out and running:
mvn clean package  install:install-file -Dfile=target/saiku-adhoc-ui-2.2-SNAPSHOT.war  -DgroupId=org.saiku -DartifactId=saiku-adhoc-ui -Dversion=2.2-SNAPSHOT -Dpackaging=war

Then checkout https://github.com/Mgiepz/saiku-adhoc.git, cd into saiku-adhoc-core and run:
mvn clean install

Then if all went well cd into saiku-adhoc-plugin and run:
mvn clean package

In the resulting "target" directory you will find a saiku-adhoc-plugin-2.2-SNAPSHOT.zip file.

Extract this into pentaho-solutions/system

There might be some confusion with the libraries responsible for CDA-Access. 
Have a look at you pentaho/web-inf/lib directory and check if there is a file that begins with
pentaho-reporting-engine-classic-extensions-cda-...
Also look at the version number of the reporting engine. If the reporting-engine has a version 3.8.x
download the jar file from
http://github.com/Mgiepz/saiku-adhoc/tree/master/lib
and put it in the lib-folder
if the reporting engine is a newer trunk-version, copy the jar file from the plugin's lib folder to 
web-inf/lib

For questions join us at ##saiku on freenode