PGROUTING_VERSION doenst control pgrouting version

[jmtaysom]

In an effort to try using postgres 10 with pgrouting 2.2.2 (because of a bug in node network) I tried switching the PGROUTING_VERSION and rebuilding but it still uses 2.5.2 since postgresql-$PG_MAJOR-pgrouting always pulls down the latest pgrouting. The only thing that I can think of doing would be to pull directly from pgrouting on github and compile from source if you wanted to specify the version.