Impala recently switched to using Python from the native toolchain for the development environment. On older versions of SLES12 (e.g. SP1), we ran into a problem where the native toolchain python didn't work, because native toolchain uses a newer SLES12 (SP3) that has a different openssl version. We should provide a way to force the development to use system python rather than the native toolchain python. This would allow flexibility on platforms not supported by the native toolchain.