r14317: Use source/bin as dir to link pam_winbind instead of source/nsswitch/

r14317: Use source/bin as dir to link pam_winbind instead of source/nsswitch/

The intention is to have the resulting binaries at one place.  This is
also usefull for upcoming changes to provide a test_pammodules rule.

With these changes I even got aware of
testsuite/nsswitch/pam_winbind_syms.exp  But this only covers
pam_winbind.