The AM_PO_SUBDIRS macro prepares the po/ directories of the
package for building. This macro should be used in internationalized
programs written in other programming languages than C, C++, Objective C,
for example sh, Python, Lisp. See Other Programming Languages for a list of programming languages that support localization
through PO files.
The AM_PO_SUBDIRS macro determines whether internationalization
should be used. If so, it sets the USE_NLS variable to ‘yes’,
otherwise to ‘no’. It also determines the right values for Makefile
variables in each po/ directory.