Support cmake build on more linux slaves
Support cmake build on more linux slaves

Default location for thirdparty_linux repo,
as installed by jenkins job lynx-updateThirdPartyLinux,
is ~/thirdparty-linux

The env variable should be optional as a way to specify
a different location rather than a mandatory step of slave
configuration.

Change-Id: I896181dbf0e1085956933478b187939fb929401c
Reviewed-on: https://gerrit.mozy.lab.emc.com/113894
Reviewed-by: Ryan Bird <962bfee7e1cfd38cfcf9a2329af3c6fe3e4b4ca9@emc.com>

mozy/mordor,mozy/mordor,mozy/mordor