FIX: cleanup build environment in failure case
FIX: cleanup build environment in failure case

cvmfs/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,djw8605/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,Gangbiao/cvmfs,reneme/cvmfs,djw8605/cvmfs,cvmfs/cvmfs,reneme/cvmfs,alhowaidi/cvmfsNDN,DrDaveD/cvmfs,djw8605/cvmfs,DrDaveD/cvmfs,djw8605/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,Gangbiao/cvmfs,Moliholy/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,Moliholy/cvmfs,alhowaidi/cvmfsNDN,alhowaidi/cvmfsNDN,Moliholy/cvmfs,reneme/cvmfs,trshaffer/cvmfs,djw8605/cvmfs,reneme/cvmfs,alhowaidi/cvmfsNDN,DrDaveD/cvmfs,Gangbiao/cvmfs,reneme/cvmfs,alhowaidi/cvmfsNDN,cvmfs/cvmfs,trshaffer/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,Moliholy/cvmfs,Moliholy/cvmfs,DrDaveD/cvmfs