android build: pin hashes of p4a recipes

contrib/android/p4a_recipes/util.py

@@ -0,0 +1,12 @@
+import os
+
+
+class InheritedRecipeMixin:
+
+    def get_recipe_dir(self):
+        """This is used to replace pythonforandroid.recipe.Recipe.get_recipe_dir.
+        If one of our local recipes inherits from a built-in p4a recipe, this override
+        ensures that potential patches and other local files used by the recipe will
+        be looked for in the built-in recipe's folder.
+        """
+        return os.path.join(self.ctx.root_dir, 'recipes', self.name)