Honor custom library paths
Honor custom library paths

Fixes compilation issue under MacOS X when not using system's default
Python installation.

Signed-off-by: Anestis Bechtsoudis <7611fa5e9fd33f993ed88a8464a47644a6f066ca@census-labs.com>

huku-/pyrsistence,huku-/pyrsistence,huku-/pyrsistence