Fix buildall to generate all the make files.

With a recent change to buildall, the command that generates all the make files from
$IMPALA_HOME was removed. This is causing builds to hang, and no target are found. I also
added the -x flag to make buildall easier to debug.

Change-Id: I33ad8f197658f932f4da01ae3186a5eede5326be
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2095
Reviewed-by: Matthew Jacobs <mj@cloudera.com>
Reviewed-by: Nong Li <nong@cloudera.com>
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: jenkins