ukify: Use VERSION_TAG instead of GIT_VERSION

GIT_VERSION isn't actually available so use VERSION_TAG instead which
is available.

src/ukify/ukify.py

@@ -50,7 +50,7 @@ from typing import (Any,
 
 import pefile  # type: ignore
 
-__version__ = '{{PROJECT_VERSION_FULL}} ({{GIT_VERSION}})'
+__version__ = '{{PROJECT_VERSION_FULL}} ({{VERSION_TAG}})'
 
 EFI_ARCH_MAP = {
     # host_arch glob : [efi_arch, 32_bit_efi_arch if mixed mode is supported]