[FIX] packaging: compute winpython path with package.py args

When building the MS Windows package, the PYTHON_VERSION variable is not
used and the WinPython path is hard coded in the Makefile and NSI file.
This prevent the usage of a newer version of Python.

With this commit, the PYTHON_VERSION is used to compute the WinPython
Python directory. That way, this directory can be derived from
package.py command line argument --vm-winxp-python-version.

Also the less windows binaries are not packaged anymore.

closes odoo/odoo#39816

Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>