seen with at least 2.7, 3.2 and 3.3:

$ python-config --libs
-lpthread -ldl -lutil -lm -lpython2.7

$ pkg-config python --static --libs
-lpthread -ldl -lutil -lpython2.7

python-config uses the SYSLIBS macro, while pkg-config uses the LIBS macro.

depending on what you want to do, both can be wrong or right:

 - to build an extension, LIBS should be used.

 - to link an embedded interpreter, SYSLIBS should be used,
   which might not be complete.
   Howver in this case MODLIBS is missing.

a patch should be easy once we can define the intended behaviour.