antimake: minor fixes
antimake: minor fixes

- Move 'ProcessTargets' before 'clean' so ifdefs in latter
  can see changes to CLEANFILES.

- Make EMBED_LIBUSUAL support srcdir != builddir

rabbitt/libusual,ifduyue/libusual,ifduyue/libusual,mgjv/libusual,markokr/libusual,ifduyue/libusual,mgjv/libusual,mgjv/libusual,mgjv/libusual,markokr/libusual,rabbitt/libusual,rabbitt/libusual,markokr/libusual,ifduyue/libusual,rabbitt/libusual,markokr/libusual