Move build-system checkout updating so it's done only once

data/tools/wesnoth/libgithub.py

@@ -576,6 +576,7 @@ def _gen(possible_dirs):
         build_system = realish_github.addon("build", readonly=True)
         return build_system, True
     bs, fresh = _get_build_system(possible_dirs)
+    bs.update()
     # Add references to shutil and os to ensure we're destructed before they are
     stored_shutil = shutil
     stored_os = os

data/tools/wesnoth/wescamp.py

@@ -66,7 +66,6 @@ if __name__ == "__main__":
             possible_build_paths.append(build_sys_dir)
         possible_build_paths.append(os.path.join(below_branch, "build-system"))
         build_system = libgithub.get_build_system(possible_build_paths)
-        build_system.update()
         init_script = os.path.join(build_system.get_dir(), "init-build-sys.sh")
 
         # Uglyness