{android,win32}/build.py: move common code to python/build/

python/build/tar.py

@@ -0,0 +1,11 @@
+import os, shutil, subprocess
+
+def untar(tarball_path, parent_path, base):
+    path = os.path.join(parent_path, base)
+    try:
+        shutil.rmtree(path)
+    except FileNotFoundError:
+        pass
+    os.makedirs(parent_path, exist_ok=True)
+    subprocess.check_call(['/bin/tar', 'xfC', tarball_path, parent_path])
+    return path