s4-python: put the python shared libs on a severe diet

s4-python: put the python shared libs on a severe diet

Our shared libs in s4 are rather bloated. Each shared lib links in
just about all our client code, making them all huge.

This hack works around the problem for the python shared libs, linking
in just the minimum code to each shared lib using a shell script
linker hack, then linking all those to glue.so

Jelmer, I know this isn't the right approach, but I'm hoping it may
inspire a better fix.

This change reduces the total size of bin/python/ from 476M to 28M on
my system

I suspect we can do the same to bin/shared/*