[xeddsa] fixed shared library copying

The copy of the build shared library was not working anymore after the
update of python2 build chain. This patch fixes it by using
self.ctx.get_site_packages_dir().

Author: goffi-contrib

pythonforandroid/recipes/xeddsa/__init__.py

@@ -24,12 +24,7 @@ def build_arch(self, arch):
                 hostpython, 'ref10/build.py',
                 _env=env
             )
-            python_version = self.ctx.python_recipe.version[0:3]
-            site_packages_dir = 'lib/python{python_version}/site-packages'.format(
-                python_version=python_version)
-            site_packages = join(self.ctx.get_python_install_dir(),
-                                 site_packages_dir)
-            shprint(sh.cp, '_crypto_sign.so', site_packages)
+            shprint(sh.cp, '_crypto_sign.so', self.ctx.get_site_packages_dir())
             self.install_python_package(arch)