relase: get failed extract-vmlinux automation back working

Only the command is back in business, but it does not work:
https://github.com/cirosantilli/linux-kernel-module-cheat/issues/79

build

@@ -553,7 +553,7 @@ Which components to build. Default: qemu-buildroot
             else:
                 git_version_tuple = tuple(
                     int(x) for x in self.sh.check_output(['git', '--version']) \
-                    .split(' ')[-1].split('.')
+                    .decode().split(' ')[-1].split('.')
                 )
                 if git_version_tuple >= (2, 9, 0):
                     # https://stackoverflow.com/questions/26957237/how-to-make-git-clone-faster-with-multiple-threads/52327638#52327638